Easykemistry

Tuesday, 28 April 2026

Carbon and Is compounds E-note

Carbon is the sixth element in the periodic table, found in period II group IV. It has an electronic configuration of 1s22s22p4.

OCCURRENCE

As a free element it occurs naturally as diamond, graphite, graphene and Fullerene in the crystalline forms. It occurs in non crysatlline forms as coal, Coke, carbon black, soot and charcoal. It also occurs in the combined state as petroleum, wood and natural gases, in minerals such as limestone (CaCO₃) and dolomite (MgCO₃), in the atmosphere as CO₂ and present as a main constituent in all plants and animals.

ALLOTROPES OF CARBON

Allotropy is the phenomenon whereby an element exists in two or more different forms in the same physical state.

The different forms of the elements are known as allotropes.

Allotropes have the same chemical properties but different physical properties.

Carbon exists in several allotropic forms:

1. Crystalline allotropes of carbon

i. Diamond

ii. Graphite

iii. Fullerenes

iv. Grephenes

(2). Non-crystalline Allotropes/Amorphous carbon

i. Coal,

ii. Charcoal

iii. Coke

iv. Lampblack and

v. Carbon black (soot)

Crystalline Allotropes of carbon

Diamond: Diamond is the purest form of carbon. In diamond each carbon atom is tetrahedrally bonded ( bonded on the four sides). The carbon atoms are closely parked and held by strong covalent bonds resulting to a giant molecule with an octahedral shape

Basic Tetrahedral Shape in Diamond Crystals

PROPERTIES OF DIAMOND

(1) It is the hardest substance know

(2) It has a high melting and boiling point because of strong covalent bond.

(3) It has a high density

(4) It is a very resistant to chemical action and temperature because all four valence electrons are saturated bonded.

(5) It is a non-conductor of electricity because there are no free valence electrons in the crystal

(6) It is transparent and high refractive index( it has the abilityto scatter light.)

USES

(1) The are used industrially for making drilling machines

(2) They are used to sharpen very hard tools.

(3) They are used for cutting glass and metals.

(4) They are also used as pivot supports in precision instruments and as dies for drawing wires

(5) They are used as jewellery

Artificial diamond: They are made by subjecting graphite to a very high temperature and pressure for several hours in the presence of nickel or rhodium catalyst.

GRAPHITE: In graphite the carbon atoms uses only 3 out of its 4 valence electrons for bonding forming flat hexagonal layers. These hexagonal layers are arranged one above the other to form a crystal lattice, each layer is bonded by weak van der walls forces of attraction.

PROPERTIES OF GRAPHITE

(1) Graphite is soft and slippery because of weak forces holding its layers. Each layer can slide over one another. Hence, graphite acts as a lubricant.

(2) It is less dense than diamond

(3) It is not affected by chemical attack (due to its open structures in layers).

(4). It is a good conductor of electricity (because of the presence of free delocalized electrons (mobile electron) in the crystal lattice.)

(5) It has high melting and boiling point.

USES

(1) It is usually used on bicycle chains and for the bearings of some motor cars.

(2) It is used as a dry lubricant.

(3) It is used as electrodes in electroplating and in dry cells.

(4) It is used to line crucibles for making high-grade steel and other alloys (since it can withstand high temperature).

(6) It is used in making lead pencils i.e. combining it with clay makes lead in pencils.

(7) It is used as a black pigment in paints.

(8) It is used as a neutron moderator in atomic piles.

INDUSTRIAL PREPARATION OF GRAPHITE

Graphite is produced industrially by heating coke in an electric furnace to a very high temperature for about 20 to 30 hours in the absence of air and under sand. This process is called the Acheson process. The graphite produced is very pure and free from grit.

DIFFERENCES IN PROPERTIES BETWEEN GRAPHITE AND DIAMOND

Graphite	Diamond
1. It has a density of 2.3gcm^-3	1. It has a density of 3.5gcm^-3
2. It is a black, opaque solid	2. It is a colourless, transparent solid
3. It is very soft, marks paper	3. It is the hardest known substance.
4. It is a good conductor of electricity	4. It is a non-conductor of electricity
5. Attacked by potassium trioxochlorate (v) and trioxonitrate (v) acid together.	5. Not attacked by these reagents.

Note: Diamond is transparent to x-rays while glass is almost opaque.

⚽ Fullerenes

Fullerenes (e.g. C₆₀) are spherical carbon molecules called buckyballs. They are used in medicine, electronics and materials science.

AMORPHOUS CARBON

These non-crystalline structures which are not considered to be true allotropes include:

CHARCOAL: This is made by burning wood, bones, or sugar in a limited supply of air. Charcoal is used to remove colour from substances. Wood charcoal is used in absorbing poisonous gases while animal charcoal is used in absorbing colours.

CARBON BLACK AND LAMP BLACK: Lamp black is obtained by burning vegetable oil lamp that it leaves a deposit of soot while carbon black is obtained from burning coal gas, natural gas or petroleum.

Carbon black and lamp black are used as an additive to rubber tyres. They are also used in making printer’s ink, carbon paper, black shoe polish, type writing.

COAL

Coal is an impure form of carbon. Coal is a complex mixture of compounds composed mainly of carbon, hydrogen and oxygen with small amounts of nitrogen, sulphur and phosphorus as impurities.

Carbonization of coal.

Coal was formed by the gradual decomposition of plant vegetation under pressure and in the absence of air under sand. A time known as the carboniferous Era. Carbon (iv) oxide, methane, and steam were liberated, leaving behind a material that contained a very high percentage of carbon.

During this process of carbonization, the vegetable material was converted in stages into several stages of coal namely

Types of Coal

There are 4 different types of coal namely:

(1) Peat-like coal: It contains about 60% of carbon by mass.

(2) Lignite coal (brown coal): It contains about 67% of carbon by mass.

(3) Anthracite coal (or hard coal): It is tough and hard. It contains about 94% of carbon by mass. Impurities present may include nitrogen, sulphur and phosphorus. Anthracite is the last stage of coal.

(4) Bituminous (soft) coal: These are use every day at home. It contains about 88% by mass of carbon.

Destructive Distillation of Coal

This is when coal is heated to a very high temperature in the absence ofair.

Yielding the following products

Coal Coal gas + Coal tar Ammoniacal liquor + Coke

Uses of coke

(i) Coke is mainly used as a fuel.

(ii) It is a very important industrial reducing agent and is used in the extraction of metals, especially iron, from their ores.

(iii) It is also used in the production of gaseous fuels, like water gas and producer gas.

(iv) It is used for the manufacture of graphite, calcium carbide, silicon carbide and carbon (iv) sulphide.

(a) Coal gas: used mainly as industrial fuel

(b) Ammoniacal liquor: is a solution of NH₃ in water. It is used to make Fertilizers

(C) Coal tar :- it is used for road construction and also to produce other chemicals like toluene, phenol, benzene, naphthalene and anthracene which are used in the synthesis of important commercial product like dyes, paints, insecticides, drugs, plastics and explosives

(d) Coke :

Distillates of Coal	Uses
1.Ammoniacal liquor	To produce (NH₄)₂SO₄ for fertilizer.
2.Coal tar	To produce useful chemicals such as phenol, benzene, disinfectants and perfumes
3.Coal gas	Used as industrial fuel.

Uses of coal

1. Coal is used mainly as fuel to generate power for steam engines, factories and electrical plants.

2. It is also used

FUEL GASES/GASIFICATION OF COKE

There are 3 types of fuel gases.

1. Producer gas: Producer gas is a mixture of nitrogen and carbon (ii) oxide. It is prepared by passing a stream of air through red hot coke.

2C_(s)h+ O_2(g) + N_2(g) 2CO_(g)+ N_2(g) + Heat

Producer gas

2. Water gas: Water gas is a mixture of hydrogen and carbon (ii) oxide gas. It is prepared by passing steam over white hot coke.

H₂O_(g) + C_(s) CO_(g) + H_2(g)

Steam white hot coke Water gas

2. Hydrogen gas:-water gas is then mixed with excess steam, and the mixture passed over iron (iii) oxide catalyst at 450⁰C.The carbon (ii) oxide decomposes the steam and the product are hydrogen and carbon (iv) oxide.

CO_(g) + H_2(g)+ H₂O_(g) CO_2(g) + 2H_2(g)

Caustic soda or water is used to absorbed carbon (iv) oxide from the mixture. Ammoniacal copper (i) chloride can be used to remove unreacted carbon (ii) oxide. The final product is hydrogen.

Differences between Producer Gas and Water Gas

(1) Producer gas has a lower heating ability than water gas. ( because water gas consists of equal volumes of hydrogen and carbon (ii) oxide both of which are combustible whereas producer gas consists of 33% combustible CO and 67% non-combustible N₂.

Water gas is an important industrial fuel and is used in the manufacture of hydrogen and other organic compounds e.g. methanol and butanol.

3. Synthetic gas: It is a mixture of hydrogen and carbon (ii) oxide gas. It is prepared by mixing steam with methane (obtained as natural gas) and passing them over Nickel catalyst at about 800⁰C.

CH_4(g) + H₂O_(g) CO_(g) + 3H_2(g)

Synthetic gas is not a major source of air pollution because sulphur is removed in the gasification process/it does not contain sulphur or sulphur compounds.

CHEMICAL PROPERTIES OF CARBON

(1) Combustion:

(a) All forms of carbon burn in excess oxygen to produce carbon (iv) oxide gas.

C_(s) + O_2(g) CO_2(g) ( Complete combustion)

(b) All forms of carbon also burn in a limited supply of air to produce carbon (ii) oxide.

C_(s) + O_2(g) CO_(g) ( Incomplete combustion)

(2) Combination reaction: Carbon combines directly with certain elements such as Sulphur, Hydrogen, Calcium and Aluminium at very high temperatures.

C_(s) + 2S_(s) CS_2(l)

Carbon (iv) sulphide

C_(s) + 2H_2(g) CH_4(g)

Methane

2C_(s) + Ca_(s) CaC_2(s)

Calcium carbide

3C_(s) + 4Al_(s) Al₄C_3(s)

Aluminium carbide.

(3) As a reducing agent: Carbon is a strong reducing agent. It reduces the oxides of the less active metals to the metals, while carbon is itself oxidized to either carbon (iv) oxide or carbon (ii) oxide, depending on the reaction conditions.

Fe₂O_3(s)+ 3C_(s) 2Fe_(s) + 3CO_(g)

2CuO_(s) + C_(s) 2Cu_(s) + CO_2(g)

(4) Reaction with strong oxidizing agents: When carbon is heated with conc. HNO₃ or conc. H₂SO₄, it is oxidized to Carbon (iv) oxide.

C_(s) + 4HNO_3(aqp 2H₂O_(l) + 4NO_2(g)+ CO_2(g)

C_(s) + 2H₂SO_4(aq) 2H₂O_(l) + 2SO_2(g)+ CO_2(g)

TOPIC: OXIDE OF CARBON.

CONTENT

· Carbon (iv) oxide

· Carbon (ii) oxide

CARBON (iv) OXIDE:- Carbon (iv) oxide is present in the atmospheric air about 0.03% by volume while in dissolved air is about 0.50% by volume.

Laboratory preparation

Carbon (iv) oxide is prepared in the laboratory by the action of dilute acids on a trioxocarbonate (iv) or a hydrogen trioxocarbonate (iv). Usually CaCO₃, in form of marble chips is used with hydrochloric acid. Reaction between CaCO₃ and HCl can be carried out in a Kipp’s apparatus.

CaCO_3(s)+ 2HCl_(aq) CaCl_2(aq)+ H₂O_(l)

2. It is also prepared by heating metallic trioxocarbonates (iv) [except those of Na and K], or the hydrogen trioxocarbonate (iv) of Na or K.

CuCO_3(s) CuO_(s) + CO_2(g)

Note: If the gas is required dry, it is pass through potassium hydrogen trioxocarbonate (iv) solution first to remove any acid fumes, and then through a U-tube containing fused Calcium chloride to remove the water vapour. The dry gas is then collected by downward delivery as it is heavier than air.

Method of collection of gases

The method of collection of gases depends on its:

1. Density.

2. Solubility.

There are two method of collecting gases:

(a) Downward delivery/upward displacement of air: This method is used for collecting gases that are denser than air e.g. CO₂, SO₂, H₂S, NO₂, Cl₂ and HCl e.t.c.

(b) Upward delivery/downward displacement of air: This method is used for collecting gases that are less denser than air e.g NH₃, H₂, N₂, methane and ethane.

INDUSTRIAL PREPARATION

CO₂ is obtained industrially as a by product in fermentation processes and when limestone is heated to make quicklime.

PHYSICAL PROPERTIES

(1) CO₂ is a colourless, odourless gas with a sharp refreshing taste.

(2) It is about 1.5 times denser than air.

(3) It is soluble in water.

(4) It turns damp blue litmus paper pink because CO₂ dissolves in water to yield trioxocarbonate (iv) acid.

(5) On cooling, it readily liquefies and solidifies (-78⁰C) to form a white solid known as dry ice.

CHEMICAL PROPERTIES

1. Reaction with water: Carbon (iv) oxide is not very active chemically. It dissolves in water to form trioxocarbonate (iv) acid (Soda water). This is a weak, dibasic acid which ionizes slightly.

(a) CO_2(g)+ H₂O_(l) H₂CO_3(aq)

(b) H₂CO_3(aq) + H₂O_(l) H₃O⁺_(aq)+ HCO₃^-_(aq)

On heating, trioxocarbonate (iv) acid decomposes to form H₂O_(l) and CO_2(g).

2. Reaction with alkalis: It reacts directly with alkalis to yield trioxocarbonate (iv)

CO_2(g)+ 2NaOH_(aq) Na₂CO_3(aq)+ H₂O_(l)

Limited

Excess CO₂ reacts with alkalis to produce Hydrogen trioxocarbonate (iv) salt.

CO_2(g) + NaOH_(aq) NaHCO_3(aq)

Excess.

3. Reaction with burning Na, K or Mg: CO₂ is reduced to carbon by burning Na, K or Mg.

CO_2(g) + 2Mg_(s) C_(s) + 2MgO_(s)

Note: CO₂ does not support combustion.

4. Reaction with red hot carbon: CO₂ is reduced to CO, If the gas is passed over red hot carbon.

CO_2(g)+ C_(s) 2CO_(g)

The reaction is of great importance in the blast furnace and in the manufacture of gaseous fuels.

Test for CO₂: Bubble the unknown gas through a solution of lime water (Calcium hydroxide)if the lime water turn milky due to the formation of insoluble calcium trioxocarbonate (iv), then the unknown gas is CO₂

Ca(OH)_2(aq)+ CO_2(g) CaCO_3(s)+ H₂O_(l).

If the gas is bubbled in excess, the milkiness disappears and turns to a clear solution due to the formation of soluble calcium hydrogen trioxocarbonate (iv).

CaCO_3(s)+ H₂O_(l) + CO_2(g) Ca(HCO₃)_(aq)

Finally, if the clear solution is heated, the milkiness reappears due to the decomposition of soluble Ca(HCO₃)₂ to form insoluble CaCO₃

Ca(HCO₃)_2(aq) CaCO_3(s)+ H₂O_(l) + CO_2(g)

Uses of carbon (iv) oxide

1. It is used as fire extinguishers since it does not support combustion.

2. It gives carbonated (aerated) drinks their refreshing taste. Beer, cider and champagne contains CO₂

3. It is used in the manufacture of Na₂CO₃ (washing soda) by the Solvay process.

4. It is used as a leavening agent in the baking of bread. Yeast and baking powder produces CO₂ which make the dough of bread to rise.

5. It is used in the manufacture of fertilizer (such as urea and (NH₄)₂SO₄.

6. Solid CO₂ (i.e dry ice) is used as a refrigerant for perishable goods e.g ice cream. (It sublimes on warming and provides a lower temperature).

7. Gaseous CO₂ is used to preserve fruits.

8. CO₂ is also used as a coolant in nuclear reactors.

CARBON (II) OXIDE

LABORATORY PREPARATION

1. Carbon (ii) oxide can be prepared by passing Carbon (iv) oxide through red-hot carbon while the Carbon (iv) oxide is itself reduced to Carbon (ii) oxide. The gaseous mixture is passed through concentrated NaOH to remove the excess Carbon (iv) oxide.

CO_2(g)+ C_(s) 2CO_(g)

The pure Carbon (ii) oxide is collected over water.

2. Carbon (ii) oxide can also be prepared by the dehydration of methanoic (formic) acid or ethanedioic (oxalic) acid, using concentrated tetraoxosulphate (vi) acid.

HCOOH_(l) ^{Conc. H2SO4} CO_(g) + H₂O

Methanoic acid

Note: The gaseous mixture is passed through concentrated NaOH to remove the CO₂.

Caution: The preparation of CO must be done in a fume cupboard as the gas is poisonous.

The major air pollutants that can result from smoky vehicles are Carbon (ii) oxide and Carbon particles.

When CO is breath in for any length of time, even 1% of it in the air may cause death, by suffocation.

PHYSICAL PROPERTIES OF CO

(1) CO is a poisonous, colourless, tasteless and odourless gas.

(2) It is insoluble in water, but dissolves in a solution of ammoniacal copper (i) chloride.

(3) It is neither lighter nor heavier than air.

(4) It is neutral to litmus.

CHEMICAL PROPERTIES OF CO

(1) As a reducing agent: CO is a strong reducing agent. It reduces some metallic oxides to the metals and it is oxidized to CO₂.

Fe₂O_3(s) + 3CO_(g) 2Fe_(s) + 3CO_2(g)

CuO_(s) + CO_(g) Cu_(s) + CO_2(g)

2. Combination reaction

(a). With oxygen: CO burns in air with a faint pale blue flame to form CO₂ .

2CO_(g) + O_2(g) 2CO_2(g)

(b). With haemoglobin: CO combine irreversibly with haemoglobin in the red blood cells to form carboxy-haemoglobin thereby preventing the red corpuscle from carry oxygen.

3j. CO combined with Chlorine gas when expose to ultra-violet light or passed over a catalyst of activated charcoal at 150⁰C to form carbonyl chloride.

CO_(g) + Cl_2(g) COCl_2(g)

This product, COCl₂, is also known as Phosgene and was employed as a poisonous gas in the First World War. It is now use in the manufacture of dyestuff.

Test for Carbon (ii) oxide

When a lighted splint is inserted into a test tube containing CO_(g) it burns with a pale blue flame and the gas produced turns lime water milky.

Uses of Carbon (ii) oxide

(1) CO is used in the extraction of metals from their ores.

(2) It is also an important constituent of gaseous fuels like producer gas and water gas.

(3) CO gas is used in the manufacture of methyl alcohol, synthetic petrol, carbonyl chloride, oxalate and formate.

WEEKEND ASSIGNMENT

1. Kipp’s apparatus is important in the laboratory because it (a) allows intermittent supply of gases. (b) is used for preparing poisonous gases. (c) is used to prepare light gas. (d) is used to prepare sensitive gas

2. Gas prepared by the reaction between methanoic acid and concentrated tetraoxosulphate (vi) acid is (a) SO₂ (b) CO (c) CO₂ (d) H₂S.

3. Gas which dissolves in ammoniacal copper (i) chloride but insoluble in water is

(a) NH₃ (b) CO (c) N₂O (d) CO₂.

4. Where else is CO₂ found in free state apart from the atmosphere?

(a) In carbonated drinks. (b) Dissolved form in water. (c) In corals. (d) In limestone region

5. It is dangerous to stay in a badly ventilated room which has a charcoal fire because of the presence of (a) carbon (ii) oxide (b) carbon (iv) oxide (c) hydrogen sulphide (d) producer gas.

THEORY

1(a) Why is the laboratory preparation of carbon (ii) oxide done in a fume chamber?

(b) State the property of CO₂ that makes it to be used in (i) carbonated drinks (ii) fire extinguishers

2(a) Why it is not advisable to stay in a closed garage for a long time when racing a car engine.

(b). State what is observed when (i) excess CO₂ is bubbled through lime water. (ii) the solution in b(i) above is heated.

TOPIC: TRIOXOCARBONATE (iv) ACID

H₂CO₃ is formed when CO_2(g)is dissolved in water. H₂CO₃ is a weak dibasic acid. It forms two series of salts:

1. Normal trioxocarbonate (iv)

2. Acidic hydrogen trioxocarbonate (iv)

Normal trioxocarbonate (iv)

Normal trioxocarbonate (iv) may be regarded as salts derived from H₂CO₃ by the complete replacement of the hydrogen by a metal or ammonium ion.

Preparation of soluble trioxocarbonates (iv)

The CO₃^2- of Na⁺, K⁺, and NH₄⁺ are soluble in water. They are prepared in the laboratory by:

Bubbling CO₂ through a solution of corresponding alkali.

2KOH_(aq) + CO_2(g) K₂CO_3(aq) + H₂O_(l)

Decomposition of corresponding hydrogen trioxocarbonates (iv).

2KHCO_3(s) K₂CO_3(aq) + H₂O_(l) + CO_2(g)

Preparation of insoluble trioxocarbonates (iv)

The insoluble metallic trioxocarbonates (iv) can be prepared by adding a solution of Na₂CO₃ or NaHCO₃ to a solution of the corresponding metallic salt.

CaCl_2(aq)+ Na₂CO_3(aq) CaCO_3(s)+ 2NaCl_(aq)

CaCl_2(aq) + 2NaHCO_3(aq) CaCO_3(s) + 2NaCl_(aq) + H2O_(l) + CO_2(g) 2AgNO_3(aq)+ Na₂CO_3(aq) Ag₂CO_3(s)+ 2NaNO_3(aq)

2AgNO_3(aq) + 2NaHCO_3(aq) Ag₂CO_3(s)+ 2NaNO_3(aq) + H₂O_(l)

Note: When preparing the CO₃^2- of the less electropositive metals like Cu, use NaHCO₃

Properties of CO₃^2- Salts

Solubility: The trioxocarbonate (iv) of alkali metal and NH₄⁺ are soluble while the other trioxocarbonate (iv) are insoluble in water.

Na₂CO_3(s)+ 2H₂O_(l) 2NaOH_(aq) + H₂CO_3(aq)

2. Action of heat: The trioxocarbonate (iv) of Na, K and Barium cannot be decomposed by heat while all other CO₃^2- decompose on heating to liberate CO_2.

ZnCO_3(s) ZnO(s) + CO_2(g)

2Ag₂CO_3(s) 4Ag_(s)+ 2CO_2(g)+ O_2(g)

(NH₄)₂CO_3(s) 2NH_3(g) + CO_2(g) + H₂O_(l)

1. Reaction with dilute acids: All trioxocarbonates (iv) react with dilute acids to form CO₂, H₂O and a salt.

Na₂CO_3(aq) + H₂SO_4(aq) Na₂SO_4(aq)+ H₂O_(l) + CO_2(g)

ZnCO_3(s) + 2HCl_(aq) ZnCl_2(aq) + H₂O_(l) + CO_2(g)

Metal	Solubility/effect of heat	Reaction with acids
K, Na	Soluble in water. Does not decompose on heating	These trioxocarbonate (iv) react with dilute acids to give a salt, water and carbon (iv) oxide.
Ca, Mg, Al, Zn Fe, Sn Pb, Cu	Insoluble in water. Decompose to yield the oxide and carbon (iv) oxide. Al₂(CO₃)₃ does not exist.
Hg, Ag Au	Insoluble in water. Decomposed to the metal, CO₂ and oxygen

Test for any CO₃^2-

The unknown substance is placed in a test-tube and dilute trioxonitrate (v) acid is added into the test tube. If a CO₃^2- is present, there will be effervescence and the gas which evolved will turn calcium hydroxide solution (lime water) milky.

CO₃^2-_(s)+ 2H⁺_(aq) H₂O_(l)

HYDROGEN TRIOXOCARBONATE (iv).

HCO₃^- may also be regarded as salts derived from H₂CO₃ by the partial replacement of the hydrogen by a metal or cationic radical.

Preparation of HCO₃^-

HCO₃^- can be prepared by passing CO₂ through a cold solution of the corresponding OH^- or CO₃^2-.

1. 2OH^-_(aq) + CO_2(g) CO₃^2-_(aq) + H₂O_(l)

2. CO₃^2-_(aq) + CO_{2 (g)}+ H₂O_(l) 2HCO₃^-_(aq)

Properties of HCO₃^-

1. Solubility: All hydrogen trioxocarbonate (IV) are soluble in water.

2. Action of heat: They can all be decomposed by heat.

2NaHCO_3(s) Na₂CO_3(s) + H₂O_(l) + CO_2(g)

3. Reaction with dilute acids: All HCO₃^- reacts with dilute acid to produce CO₂, H₂O and a salt. 2NaHCO_{3 (aq)} + H₂SO_{4 (aq)} Na₂SO_4(aq) + 2H₂O_(l) + 2CO_2(g)

NOTE: This reaction is used to test for HCO₃^-

COAL at a glance

SEO Keywords

Coal formation stages
Types of coal and uses
Properties of coal
Coalification process
Anthracite vs bituminous coal
Fossil fuels explained

Introduction

Coal is a fossil fuel formed from the remains of plants that lived millions of years ago. It is mainly composed of carbon and is one of the most important sources of energy used for electricity generation and industrial processes.

Coal is formed through a slow process called carbonization, where plant materials are buried under sediments and exposed to heat and pressure over time.

Formation of Coal

Coal formation began during ancient geological periods such as the , when dense forests existed.

Process of Formation

Plants absorb carbon dioxide during photosynthesis.
Dead plants accumulate in swampy areas.
Layers of sediment cover the plant material.
Heat and pressure increase over millions of years.
Gradual conversion into different forms of coal.

Stages of Coal Formation (Coalification)

Coal forms in stages, with increasing carbon content and energy value:

1. Peat This is the first stage of coal formation ( also known as coal in the making)

It Contains partially decayed plant material

i. It has Low carbon content (~50–60%)

High moisture content
Burns with a lot of smoke

2. Lignite (Brown Coal)

Soft and brown in color
Higher carbon content than peat (~60–70%)
Low heating value
Contains moisture

3. Bituminous Coal

Most commonly used coal
Black and relatively hard
Higher carbon content (~70–85%)
Produces more heat
Used in industries and electricity generation

4. Anthracite

Highest grade of coal
Very hard and shiny
Highest carbon content (~90–95%)
Burns with a clean, smokeless flame
Highest energy value

Types of Coal

Coal is generally classified based on its carbon content and energy value:

Type	Carbon Content	Characteristics	Uses
Peat	Low	Soft, moist	Limited fuel
Lignite	Moderate	Brown, crumbly	Power generation
Bituminous	High	Black, widely available	Industrial fuel
Anthracite	Very high	Hard, clean burning	Domestic & industrial

Properties of Coal

1. Physical Properties

Color: Brown to black
Texture: Soft (peat) to hard (anthracite)
Lustre: Dull to shiny
Density: Increases with carbon content

2. Chemical Properties

Mainly composed of carbon, with hydrogen, oxygen, nitrogen, and sulfur
Produces carbon dioxide (CO₂) when burned
May release sulfur compounds causing pollution

3. Combustion Properties

Burns to produce heat energy
Calorific value increases from peat → anthracite
Some types produce smoke and soot

4. Coking Property

Certain coals (especially bituminous) can soften and form coke when heated in the absence of air
Coke is used in iron and steel production

Uses of Coal

Generation of electricity in power plants
Production of coke for metallurgy
Industrial fuel
Production of chemicals such as coal tar and ammonia

Advantages of Coal

Abundant and relatively cheap
High energy output
Easy to store and transport

Disadvantages of Coal

Non-renewable resource
Causes air pollution (CO₂, SO₂ emissions)
Contributes to global warming
Mining can damage the environment

Conclusion

Coal remains a major energy source worldwide despite environmental concerns. Understanding its stages, types, and properties helps explain its wide range of uses and its impact on the environment.

Objectives questions

Coal is primarily composed of
A. Hydrogen
B. Carbon
C. Oxygen
D. Nitrogen

The process by which coal is formed from plant remains is called
A. Distillation
B. Carbonization
C. Combustion
D. Crystallization

Which of the following is the lowest grade of coal?
A. Anthracite
B. Bituminous
C. Lignite
D. Peat

The highest grade of coal with the highest carbon content is
A. Lignite
B. Peat
C. Anthracite
D. Coke

Which type of coal is most commonly used in industries?
A. Peat
B. Lignite
C. Bituminous
D. Anthracite

Coal that burns with little or no smoke is
A. Lignite
B. Bituminous
C. Anthracite
D. Peat

The stage that comes immediately after peat in coal formation is
A. Anthracite
B. Lignite
C. Coke
D. Charcoal

Which of the following products is obtained from coal processing?
A. Ethanol
B. Coal tar
C. Glucose
D. Methane

The formation of coke from coal involves heating in the absence of
A. Water
B. Oxygen
C. Nitrogen
D. Hydrogen

Which of the following is a disadvantage of coal?
A. High energy output
B. Easy storage
C. Causes air pollution
D. Abundant supply

Answer Key

Here’s a clear, student-friendly blog note you can use:

Carbon and Its Allotropes

Introduction

Carbon is a unique and versatile element found in Group 14 of the periodic table. It has the atomic number 6 and is known for its ability to form a wide variety of compounds. This is mainly due to its property of catenation (the ability to bond with itself) and its ability to form single, double, and triple covalent bonds.

Carbon exists in different structural forms known as allotropes.

What Are Allotropes?

Allotropes are different physical forms of the same element in the same state.

These forms have different arrangements of atoms, leading to different properties.

Allotropes of Carbon

Crystalline Allotropes

1. Diamond

Diamond is one of the most well-known allotropes of carbon.

Structure:

i. Each carbon atom is bonded to four other carbon atoms in a tetrahedral arrangement (sp³ hybridization) giving diamond an octahedral shape

ii. Forms a rigid 3D network.

Properties:

i. It is the Hardest natural substance known

ii.High melting point

iii. It does not conduct electricity ( because it does not contain free mobile electrons)

iv. It is Transparent and has a brilliant shine

Uses:

Jewelry
Cutting and drilling tools

2. Graphite

Graphite is another common allotrope of carbon.

Structure:

i. Each carbon atom is bonded to three other carbon atoms in a planar hexagonal structure (sp² hybridization).

ii. Layers are held together by weak van der walls forces and can slide over each other. ( hence Graphite is used as a dry lubricant)

Properties:

i. It is Soft and slippery

ii. It Conducts electricity ( due to the presence of free mobile electrons)

iii. It is Black and opaque

Uses:

i. It is used on making "lead"Pencil

ii. It is as a dry Lubricant

iii. It is used as Electrodes in batteries

3. Graphene

Graphene is a single layer of graphite.

Structure:

This is a One-atom-thick sheet of carbon atoms arranged in a hexagonal lattice.

Properties:

i. it is Extremely strong

ii. It is an Excellent conductor of heat and electricity

iii. It us Very light and flexible

Uses:

i. It is used in Electronics

ii. It is used as Sensors

iii. Advanced materials

4. Fullerenes

Fullerenes are molecules made entirely of carbon, shaped like hollow spheres, tubes, or ellipsoids.

Examples:

Buckminsterfullerene (C₆₀), also called “buckyballs”

Properties:

i Lightweight

ii. Good electrical properties

iii. Can act as antioxidants

Uses:

i. It is used in Drug delivery systems

ii. It is used in Nanotechnology

iii. It is used as Lubricants

5. Carbon Nanotubes

These are cylindrical structures made from rolled-up sheets of graphene.

Properties:

i. Very strong

ii. Excellent electrical conductivity

iii. High thermal stability

Uses:

i. It is used in Electronics

ii. Reinforcing materials

iii. Energy storage devices

Amorphous Forms of Carbon

These do not have a definite crystalline structure.

Examples:

i. Coal

ii. Charcoal

iii. Coke

iv. Soot

Uses:

Fuel
Filtration (activated charcoal)
Industrial processes

Conclusion

Carbon is one of the most important elements in chemistry due to its versatility. Its allotropes, ranging from the hardest substance (diamond) to soft graphite and advanced materials like graphene, demonstrate how structure influences properties. These forms play vital roles in everyday life and modern technology.

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Hydrogen and Its Compounds

Hydrogen is the lightest and simplest element in the periodic table.

i. Symbol: H

ii. Atomic number: 1

iii. Electronic configuration: 1s¹

It is a colourless, odourless, and tasteless gas.

Hydrogen is unique because it can behave like both:

i. Alkali metals (Group I) → loses 1 electron

ii. Halogens (Group VII) → gains 1 electron

Occurrence of Hydrogen

Hydrogen is the most abundant element in the universe, but it is not found as a free element on Earth. It occurs mainly in the combined state in:

i. Water (H₂O)

ii. Hydrocarbons (petroleum, natural gas)

ii. Acids and organic compounds

Laboratory Preparation of Hydrogen

Hydrogen is commonly prepared by reacting metals with dilute acids:

Zn + 2HCl → ZnCl2 + H2

Apparatus used:

Conical flask
Delivery tube
Water trough (for collection)

Industrial Preparation of Hydrogen

(a) Electrolysis of Water

Water is decomposed into hydrogen and oxygen using electricity.

(b) Steam Reforming

Methane reacts with steam at high temperature:

CH4 + H2O → CO + 3H2

Physical Properties of Hydrogen

i. Colourless, odourless gas

ii. Very light (least dense gas)

iii. Slightly soluble in water

iv. Highly combustible

Chemical Properties of Hydrogen

(a) Combustion

Hydrogen burns in oxygen to form water:

2H2 + O2 → 2H2O

(b) Reducing Property

Hydrogen reduces metal oxides:

CuO + H2 → Cu + H2O

(c) Reaction with Non-metals

i. With chlorine → HCl

ii. With nitrogen → NH₃

Uses of Hydrogen

i. Manufacture of ammonia (Haber Process)

ii. Hydrogenation of oils (margarine production)

iii. Fuel (rocket fuel, clean energy)

iv. Welding (oxy-hydrogen flame)

Activity Series of Hydrogen

This is an arrangement of metals based on their ability to displace hydrogen from cold water, steam or acids. The activity series helps us predict whether a metal can displace hydrogen from acids.

Activity Series (Simplified)

K, Na, Ca, Mg, Al, Zn, Fe, Pb, H, Cu, Ag, Au

Key Idea:

1. Metals above hydrogen → react with dilute acids to produce hydrogen gas

2. Metals below hydrogen → do NOT produce hydrogen gas

Examples:

Zinc + Acid → Hydrogen produced
Copper + Acid → No reaction

Important Reactions

Zn + H2SO4 → ZnSO4 + H2

Cu + HCl → (No reaction)

Compounds of Hydrogen

1. Water (H₂O)

Properties:

i. Colourless liquid

ii. Neutral (pH ≈ 7)

iii. Universal solvent

Uses:

i. Drinking

ii. Industrial cooling

iii. Chemical reactions

2. Hydrogen Chloride (HCl)

i. It is a colourless gas with pungent smell

ii. It is forms hydrochloric acid in water

Uses:

i. Cleaning metals

ii. Laboratory reagent

3. Ammonia (NH₃)

i. It is a colourless gas with sharp pungent smell

ii. It is highly soluble in water

Uses:

i. It is used in manufacturing Fertilizers

ii. It is used as aRefrigeration

iii. It is used as Cleaning agents

4. Hydrogen Sulphide (H₂S)

i. Colourless gas with rotten egg smell

ii. Toxic and poisonous

Test:

Turns lead(II) ethanoate paper black

5. Methane (CH₄)

i. Simplest hydrocarbon

ii. Main component of natural gas

Uses:

i. Fuel

ii. Chemical production

6. Safety Precautions

i. Hydrogen is highly flammable → avoid open flames

ii. H₂S is toxic → handle in well-ventilated areas

iii. Always test gases properly in the lab

Summary

i. Hydrogen is the lightest element and very reactive

ii. It acts as a reducing agent

iii. Metals above hydrogen in the activity series produce H₂ gas

iv. Important compounds include water, ammonia, HCl, H₂S,

SULPHUR AND ITS COMPOUNDS at a glance

SULPHUR

Sulphur is found in group VI period II in the Periodic Table. It occurs as a free element found in underground deposits. It is also found in the combined state as metallic Sulphide and as tetraoxosulphate (IV).

ELECTRONIC STRUCRURE OF SULPHUR

Extraction of Sulphur by the Frasch Process

The Frasch Process is an industrial method used to extract sulphur from underground deposits. It is especially useful when sulphur is found deep below the earth’s surface, making traditional mining difficult.

In this process, a set of three concentric pipes is drilled down into the sulphur deposit. Superheated water (at about 160–170°C) is pumped through the outermost pipe to melt the sulphur underground, since sulphur has a relatively low melting point.

Next, hot compressed air is forced down the innermost pipe. This creates pressure that pushes the molten sulphur up through the middle pipe to the surface.

The sulphur obtained is usually very pure (about 99.5%) and requires little further purification.

Key Advantages

I. Produces high-purity sulphur

ii. Reduces the need for traditional mining

iii Efficient for deep underground deposits

Simple Summary

The Frasch Process melts underground sulphur using hot water and then forces it to the surface using compressed air.

ALLOTROPES OF SULPHUR

There are two main crystalline allotropes of Sulphur they are: -

1 Rhombic Sulphur: This is a bright yellow octahedral crystalline solid made up of S₈ molecules. It is stable below 96^oC.

2 Monoclinic Sulphur: This is a needle like crystalline molecule consisting of S8. It has an amber colour and is stable at temperatures above 96^oC. It easily reverts to Rhombic below 96^oC. The transition temperature between Rhombic and Monoclinic is 96^oC.

Comparison of the Physical Properties of Rhombic and Monoclinic Sulphur

	Rhombic sulphur	Monoclinic sulphur
Colour	Bright yellow	Amber
Shape	Octahedral	Needle-shaped
Density	2.80 g/cm³	1.98g/cm³
Melting point	113⁰C	119^oC
Stability	Stable below 96^oC	Stable above 96^oC

There are other non crysatlline allotropes of Sulphur such as

1. Amorphous sulphur: formed when sulphur is dissolved in carbon(IV) sulphide and the solution is allowed to evaporate.

2. Plastic sulphur: formed when molten Sulphur is suddenly poured into cold water:00

PHYSICAL PROPERTIES

1. Sulphur is a yellow solid.

2. It melts at 119^oC and boils at 444^oC

3. It is insoluble in water but soluble in carbon (IV) sulphide and toluene

3. It is a poor – conductor of heat and electricity.

CHEMICAL PROPERTIES

1. It reacts directly with metals to form sulphide (S^2-)

Fe_(s) + S_(s) → FeS_(s)

2 It reacts with hydrogen to form hydrogen sulphide;

H_2(g) + S_(s) → H₂S_(g)

3. It reacts with excess oxygen to form sulphur (IV) oxide

O_2(g) + S_(s) →SO_2(g)

4. It reacts with coke (carbon) to form carbon (II) sulphide

C(s) + S(s) → CS2

USES

1. It used in manufacturing tetraoxosulphate (IV) acid

2. It used in vulcanization of rubber

3. It used as germicides

4. It used in manufacturing bleaching agent

COMPOUNDS OF SULPHUR

1. HYDROGEN SULPHIDE, H2S

Hydrogen sulphide is found in volcanic gases, sulphur springs, coal gas and natural gas.

LABORATORY PREPARATION

Hydrogen sulphide is prepared in the laboratory by the action of dilute acids on metallic sulphide like Iron (II) sulphide

2HCl_(aq)+ FeS_(s) → FeCl_2(aq) + H₂S_(g)

The Kipp’s apparatus is used for regular supply of hydrogen sulphide in the laboratory.

PHYSICAL PROPERTIES of Hydrogen sulphide

1. It is a colourless gas

2. It smells like that of rotten egg.

2. It is a poisonous gas

3. It is about 1.18 times denser than air.

4. It is moderately soluble in water to form very weak acidic solution.

5. It burns with pale blue flame.

CHEMICAL PROPERTIES

1. As an acid it reacts with alkali to form a normal salt and water

2NaOH_(aq) + H₂S_(g) → Na₂S_(aq) +2H₂O_(l)

2. It reacts with excess oxygen to form sulphur (VI) oxide but forms deposit of sulphur with limited oxygen

2H₂S_(g) + 3O_2(g) → 2H₂O_(l) + 2SO_2(g)

2H₂S_(g) + O_2(g) → 2H_2(l) + 2S_(s)

3. As a reducing agent, it reacts with many oxidizing agents such as acidified KMnO₄, acidified K₂Cr₂O₇, chlorine gas, FeCl₂, SO₂, H₂SO₄ and HNO₃

TEST FOR HYDROGEN SULPHIDE

Moistened a piece of filter paper with lead (II) trioxonitrate (V) solution and dropped it into a gas jar of the unknown gas. If the paper turns black, then the gas is H₂S.

SULPHUR (IV) OXIDE, SO₂

LABORATORY PREPARATION

It is prepared in the laboratory by heating sodium or potassium trioxosulphate (IV) with tetraoxosulphate (VI) acid or hydrochloric acid.

Na₂SO_3(aq)+2HCl_(aq) → 2NaCl_(aq)+ H₂O(l) + SO_2(g)

Physical Properties of sulphur (IV) oxide

1. Sulphur (IV) oxide is a colourless poisonous gas.

2. It smell like that of burning matches.

2. It is very soluble in water.

3. It is about 2.5 times denser than air.

Chemical Properties

1. As an acid: - it reacts with alkali to form normal salt and water only.

2NaOH_(aq)+ SO_2(g) → Na₂SO_3(aq) + H₂O_(l)

2. As reducing agent: - Sulphur (IV) oxide reduces oxidizing agents such as acidified KMnO₄; acidified K₂Cr₂O₇; FeCl₃, HNO₃, chlorine gas. It decolorizes acidified purple KMnO₄ and turns acidified orange K₂Cr₂O₇ to green.

3. As an oxidizing agent: -Sulphur (IV) oxide reacts as oxidizing agent in the presence of strong reducing agent such as hydrogen sulphide.

2H₂S_(g) + SO_2(g) → 2H₂O_(l) + 3S_(s)

C_(s)+ SO_2(g)→CO_2(g)+ S_(s)

4. As a bleaching agent: - It decolourising dye by its bleaching action. The bleaching action is similar to that of chlorine becausewater must be present.

But, while chlorine bleaches by oxidation sulphur IV oxide bleaches by reduction.

USES of sulphur (IV) oxide

1.It is used in manufacture of tetraoxosulphate (VI) acid.

2. It is used as a germicide and a fumigant especially for destroying termites.

3. It is used as bleaching agent for straw, silt and wood.

4. It is used as preservative in some liquid e.g orange juice.

5. Liquid sulphur (IV) oxide is used as refrigerant.

Test for SO2

1. When sulphur (IV) oxide gas is bubbled through a solution of either acidified potassium heptaoxodichromate (VI) or potassium tetraoxomanganate (VII), it changes the colour of acidified K₂Cr₂O₇ from orange to green or it changes the colour of acidified KMnO₄ purple to colourless.

SULPHUR (VI) OXIDE, SO₃

Sulphur (VI) oxide is prepared by reacting sulphur (IV) oxide and oxygen at 450^oC and 1 atm pressure in the presence of vanadium (V) oxide or platinized asbestos as catalyst

2SO_2(g) + O_2(g) →2SO_3(g)

PHYSICAL PROPERTIES OF SO₃

1. It is a white needle-like crystal at room temperature.

2. It has a low boiling point and vapourizes on gentle heating.

3 It dissolves readily in water to give tetraoxosulphate (VI) acid.

TRIOXOSULPHATE (IV) ACID, H₂SO₃

Trioxosulphate (IV) acid is a dibasic acid with a molecular formula H₂SO₃

Laboratory Preparation OF H₂SO₃

It is prepared in the lab by the action of dilute hydrochloric acid on heated sodium trioxosulphate (IV) to produce sulphur (IV) oxide, which is then dissolved in water.

Na₂SO_3(s)+2HCl_(aq)→2NaCl_(aq) + H₂O_(l) + SO_2(g)

H₂O_(l)+ SO_2(g) → H₂SO_3(aq)

Sulphur (IV) Oxide is the acid anhydride of trioxosulphate (IV) acid.

PHYSICAL PROPERTIES OF H₂SO₃

1. It is colourless liquid.

2. It is readily soluble in water.

3. It has an irritating and choking smell.

Chemical Properties oF H₂SO₃

1. It reacts with alkalis to form salt and water.

2NaOH_(aq) + H₂SO_3(aq)→ Na₂SO_3(aq)+ 2H₂O_(l)

2. It oxidises in air to tetraoxosulphate (VI) acid

2H₂SO_3(aq)+ O_2(g) → 2H₂SO_4(aq)

3. As a reducing agent: - It reduces oxidizing agent like acidified KMnO₄and acidified K₂Cr₂O₇

4 It bleaches dyes in the presence of water.

Test for SO₃^2-

Add a little amount of barium chloride solution to a solution of the unknown substance. If a white precipitate is formed which is soluble in dilute hydrochloric acid then the presence of a trioxosulphate (IV) ion is confirmed.

USES OF H₂SO₃

1. It is used for bleaching straw and other fabrics.

2. It is used as a germicide.

TETRAOXOSULPHATE VI ACID, H₂SO₄

Tetraoxosulphate VI acid is one of the most important chemical compounds known. It is used in almost every manufacturing process; hence it is mostly prepared industrially.

INDUSTRIAL PREPARATION OF H₂SO₄

It is manufactured industrially by Contact process. The following equations summarizes the steps involved in the Contact process.

1. Sulphur is burnt in dry air to obtain sulphur (IV) oxide, SO₂

S_(s) + O_2(g) → SO₂(g)

2.The Sulphur (IV) oxide produced is combined with excess oxygen in the presence of vanadium V oxide (V₂O₅ ) as catalyst at a temperature of 450^oC to yield sulphur (VI) oxide.

SO₂(g) + O_2(g) → 2SO_3(g) + heat

3. The sulphur (VI) oxide is then dissolved in concentrated H₂SO₄ to produce a thick oily liquid called Oleum.

H₂SO_4(aq) + SO_3(g)→ H₂S₂O_7(aq)

4. The Oleum is then combined with one mole of water to produce about 98% tetraoxosulphate (VI) acid.

H₂O_(l)+ H₂S₂O_7(aq)2H₂SO_4(aq)

NOTE: Dissolving Sulphur (VI) oxide in water directly is highly exothermic and will cause the acid to vaporize, producing a mist of droplets of the concentrated acid which can spread and cause acid burns.

PHYSICAL PROPERTIES

1. It is a colourless, viscous liquid with density of 1.84gcm^-3

2. It is corrosive and cause burns when in contact with the skin.

3. It is highly soluble in water evolving large amount of heat.

CHEMICAL PROEPERTIES

1. As an acid,

i. It reacts with metals higher than hydrogen in the electrochemical series to liberate hydrogen gas

Mg_(s)+ H₂SO_4(aq)→ MgSO_4(aq)+ H_2(g)

ii. It reacts with bases to form salts and water ZnO_(s)+H₂SO_4(aq) →ZnSO_4(aq)+H₂O_(l)

iii. It reacts with alkali to form normal and acidic salt

H₂SO_4(aq)+KOH_(aq)→NaHSO_4(aq)+ H₂O_(l)

H₂SO_4(aq)+ KOH_(aq)→ Na₂ SO_4(aq) + 2H₂O_(l)

iv.. It reacts with trioxocarbonate (IV) to liberate carbon (IV) oxide

H₂SO_4(aq)+CuCO_3(aq)→CuSO_4(aq)+ H₂O_(l) + CO_2(g)

2. As oxidizing agent: - Concentrated H₂SO₄ oxidise metals and non –metals to yield the corresponding tetraoxosulphate VI and itself reduced to SO2. It oxidises hydrogen sulphide to Sulphur.

Cu_(s)+ 2H₂SO_4(aq)→ CuSO_4(aq)+ 2H₂O_(l)+SO_2(g)

C_(s) + 2H₂SO_4(aq)→2H₂O_(l)+ CO_2(g)+ 2SO_2(g)

H₂SO_4(aq)+ H₂S_(g)→S_(s)+H₂O_(l)+ SO_2(g)

3. As a dehydrating agent: - Concentrated tetraoxosulphate (VI) acid also behaves as a dehydrating agent, removing components of water from compounds like sugar and ethanedioic acid

C₁₂H₂₂O_11(s)→12C_(s)+11H₂O_(l)

^{sugar charcoal}

COOH

| + H2SO4 → CO2 + CO + H2O

COOH conc

4. Concentrated tetraoxosulphate (VI) displaces volatile acids from their salts

NaCl_(s)+H₂SO_4(aq)→NaHSO_4(aq) + HCl_(g)

Test for SO₄^2-

Add Barium chloride solution to a solution of the unknown salt. If a white precipitate is formed which is insoluble in excess dilute hydrochloric acid, then the presence of a tetraoxosulphate (VI) ion is confirmed.

USES OF H₂SO₄

1. It is used as an electrolyte in lead accumulator.

2. It is used in production of fertilizers e.g ammonium tetraoxosulphate (VI).

3. It is used in purification of crude oil.

4. It is used as drying agent for many gases except NH₃ and H₂S gas.

5 It is used to clean metals before electroplating.

6. It is used in the production of fibres

7. It is used in the manufacture of synthetic detergents

TETRAOXOSULPHATE (VI) SALTS: -

These are the salts formed when metals, bases or alkalis and trioxocarbonate IV reacts with H2SO4

USES OF TETRAOXOSULPHATE (VI) SALTS

1. Ammonium tetraoxosulphate (VI) (NH4)2SO4 used as fertilizers

2. Sodium tetraoxosulphate (VI) (Na2SO4) is used in paper manufacture and as a purgative

3. Calcium tetraoxosulphate (VI) (CaSO4) is mined as gypsum and is used as plaster of Paris (POP) used to set broken bones.

4. Aluminum tetraoxosulphate (VI) (Al2(SO4)3) is used to coagulate precipitate in purification of water (alum)

5. Iron II tetraoxosulphate (VI) is used to treat anemia.

OBJECTIVE QUESTIONS

1. Sulphur belongs to which group in the periodic table?
A. Group I
B. Group IV
C. Group VI
D. Group VII

2. The most common allotrope of sulphur at room temperature is:
A. Monoclinic sulphur
B. Plastic sulphur
C. Rhombic sulphur
D. Amorphous sulphur

3. Which colour is associated with sulphur?
A. Red
B. Yellow
C. Blue
D. Green

4. Sulphur is mainly extracted using the because:
A. It is cheap
B. It produces impure sulphur
C. Sulphur is found underground
D. It requires no heat

5. Which of the following is NOT an allotrope of sulphur?
A. Rhombic
B. Monoclinic
C. Plastic
D. Diamond

6. Sulphur dioxide has the chemical formula:
A. SO
B. SO₂
C. SO₃
D. S₂O

7. The oxidation state of sulphur in SO₂ is:
A. +2
B. +4
C. +6
D. −2

8. Sulphur dioxide acts mainly as a:
A. Reducing agent
B. Oxidizing agent
C. Catalyst
D. Base

9. Which gas is formed when sulphur burns in air?
A. Hydrogen sulphide
B. Sulphur trioxide
C. Sulphur dioxide
D. Carbon dioxide

10. The gas with a rotten egg smell is:
A. SO₂
B. H₂S
C. CO₂
D. NH₃

11. Hydrogen sulphide turns lead(II) ethanoate paper:
A. Blue
B. Red
C. Black
D. White

12. The contact process is used in the manufacture of:
A. Hydrochloric acid
B. Nitric acid
C. Sulphuric acid
D. Carbonic acid

13. The catalyst used in the is:
A. Iron
B. Nickel
C. Vanadium(V) oxide
D. Platinum

14. Oleum is a solution of:
A. SO₂ in water
B. SO₃ in H₂SO₄
C. H₂SO₄ in water
D. SO₂ in H₂SO₄

15. Sulphuric acid is best described as:
A. Weak acid
B. Strong acid
C. Neutral compound
D. Organic acid

16. Which of the following reacts with dilute sulphuric acid to produce hydrogen gas?
A. Copper
B. Zinc
C. Silver
D. Gold

17. The drying agent commonly used in laboratories is:
A. NaCl
B. H₂SO₄ (conc.)
C. HCl
D. NaOH

18. Sulphur trioxide reacts with water to form:
A. H₂SO₃
B. H₂SO₄
C. H₂S
D. SO₂

19. Acid rain is mainly caused by:
A. CO₂
B. SO₂
C. O₂
D. H₂

20. Plastic sulphur is formed when:
A. Sulphur is slowly cooled
B. Molten sulphur is rapidly cooled
C. Sulphur reacts with oxygen
D. Sulphur is heated gently

THEORY QUESTIONS

(I). Name the process represented by the chart

ii). Identify reactant X and product Y.

iii). What are the operating temperature and pressure at stage II

iv). Mention the stage which requires a catalyst and state the catalyst used.

v) give the reason why the SO3 produced in stage II is not dissolved directly in water.

2.(a). State two physical properties of hydrogen sulphide

(ii). Name the laboratory equipment used for intermittent production of hydrogen sulphide?

b. What property of hydrogen sulphide is illustrated in the reaction represented by the following equation?

H2S + 2NaOH ---> Na2S + H2O

Answer Key

Thursday, 16 April 2026

SOLUBILITY at a glance

Solubility:

Solubility of a solute in a solvent is the maximum amount of a solute in moles or in grams that can dissolve/ saturate 1dm3 of solution at a particular temperature.

For example, sugar dissolving in water is a common illustration of solubility.

Solubility of a solute depends on several factors:

i. Nature of solute and solvent: “Like dissolves like” — polar substances dissolve in polar solvents, and non-polar in non-polar.

ii. Temperature: For most solid solutes, solubility increases with increase in temperature, while for gases solubility generally decreases with increase in temperature

iii. Pressure: Mainly affects gases; higher pressure increases the solubility of gases in liquids.

A solution can be:

i. Unsaturated : one that can still dissolve more solute at a particular temperature.

ii. Saturated : one that contains the maximum amount of solute it can hold at a particular temperature in the presence of undissolved solute particles

iii. Supersaturated : one that contains more solute than it can normally hold at a particular temperature (and is unstable).

Determination of Solubility

Solubility is commonly determined experimentally by preparing a saturated solution at a known temperature and then

Weigh the remaining solute.

Solubility is then calculated using:

Solubility= Mass of solute x 100

Mass of solvent

It is often expressed as grams of solute per 100 g of solvent.

A solubility curve is a graph that shows how the solubility of a substance changes with temperature.

To generate a solubility curve for salts like NaCl, Na₂SO₄, KNO₃, Na₂CO₃, and Ca(OH)₂, we usually rely on experimental data plotted as a graph.

Sample Solubility Data (g per 100 g of water)

Temperature (°C)	NaCl	KNO₃	Na₂SO₄	Na₂CO₃	Ca(OH)₂
0.	36	13	5	7	0.19
20	36	32	20	22	0.17
40	37	64	45	48	0.14
60	37	110	30	50	0.12
80	38	170	10	46	0.10
100	39	245	5	45	0.08

How the Solubility Curves Look

If you plot this data (Temperature on x-axis, Solubility on y-axis), you’ll observe:

NaCl (Sodium chloride)
Almost a flat line → solubility changes very little with temperature.
KNO₃ (Potassium nitrate)
A steep upward curve → solubility increases rapidly with temperature.
Na₂SO₄ (Sodium sulfate)
Shows a peak (unusual behavior) → increases up to about 40°C, then decreases (due to change in crystal form).
Na₂CO₃ (Sodium carbonate)
Moderate increase, then slightly levels off at higher temperatures.
Ca(OH)₂ (Calcium hydroxide)
Downward slope → solubility decreases as temperature increases (rare for solids).

A combined solubility curve for different salts highlights how substances respond differently to temperature changes.

While most solids like KNO₃ become more soluble at higher temperatures, some like Ca(OH)₂ show the opposite trend.

Others, like NaCl, remain nearly constant. These variations are important in industrial processes, crystallization, and chemical separation techniques.

Objective Questions

Solubility is defined as the: A. Rate of dissolving a solute
B. Maximum amount of solute dissolved in a solvent at a given temperature
C. Amount of solvent in a solution
D. Volume of solution formed

A solution that can dissolve more solute is said to be: A. Saturated
B. Supersaturated
C. Unsaturated
D. Concentrated

Which of the following factors does NOT affect solubility? A. Temperature
B. Pressure
C. Nature of solute
D. Colour of solute

The solubility of most solid substances in water generally: A. Decreases with temperature
B. Increases with temperature
C. Remains constant
D. Becomes zero

The solubility of gases in liquids: A. Increases with temperature
B. Decreases with temperature
C. Is unaffected by temperature
D. Becomes constant

Increasing pressure increases the solubility of: A. Solids in liquids
B. Liquids in liquids
C. Gases in liquids
D. Solids in gases

A supersaturated solution is: A. Stable
B. Contains less solute than required
C. Contains more solute than it can normally hold
D. Cannot exist

“Like dissolves like” means: A. All substances dissolve in water
B. Polar dissolves polar, non-polar dissolves non-polar
C. Solids dissolve only in solids
D. Liquids dissolve only in gases

Which of the following is an example of a saturated solution? A. Contains no solute
B. Contains maximum solute at a given temperature
C. Contains excess solvent
D. Contains only gas

The unit of solubility is commonly expressed as: A. mol/dm³
B. g/dm³
C. g per 100 g of solvent
D. kg/m³

A solubility curve shows the relationship between: A. Pressure and volume
B. Temperature and solubility
C. Mass and density
D. Volume and pressure

On a solubility curve, a point below the curve represents: A. Saturated solution
B. Supersaturated solution
C. Unsaturated solution
D. Boiling solution

Which substance shows little change in solubility with temperature? A. KNO₃
B. NaCl
C. NH₃
D. CO₂

Which of the following has decreasing solubility with increase in temperature? A. NaCl
B. KNO₃
C. Ca(OH)₂
D. Na₂CO₃

A point above the solubility curve represents: A. Unsaturated solution
B. Saturated solution
C. Supersaturated solution
D. Dilute solution

Solubility depends on: A. Colour only
B. Temperature and nature of substances
C. Shape of container
D. Time of day

When a saturated solution is cooled, crystals may form because: A. Solubility increases
B. Solubility decreases
C. Pressure increases
D. Volume increases

Which of the following best describes a solution? A. A mixture of two solids
B. A homogeneous mixture
C. A heterogeneous mixture
D. A suspension

The process of obtaining solid crystals from a solution is called: A. Filtration
B. Evaporation
C. Crystallization
D. Distillation

Which of the following is least soluble in water at room temperature? A. NaCl
B. KNO₃
C. Ca(OH)₂
D. Na₂CO₃

easykemistry

Tuesday, 28 April 2026

Carbon and Is compounds E-note

⚽ Fullerenes

COAL at a glance

SEO Keywords

Introduction

Formation of Coal

Process of Formation

Stages of Coal Formation (Coalification)

1. Peat This is the first stage of coal formation ( also known as coal in the making)

It Contains partially decayed plant material

i. It has Low carbon content (~50–60%)

2. Lignite (Brown Coal)

3. Bituminous Coal

4. Anthracite

Types of Coal

Properties of Coal

1. Physical Properties

2. Chemical Properties

3. Combustion Properties

4. Coking Property

Uses of Coal

Advantages of Coal

Disadvantages of Coal

Conclusion

Answer Key

Carbon and Its Allotropes

Introduction

What Are Allotropes?

Allotropes of Carbon

1. Diamond

2. Graphite

3. Graphene

4. Fullerenes

5. Carbon Nanotubes

Amorphous Forms of Carbon

Conclusion

SEO Keywords

Hydrogen and Its Compounds

Zn + 2HCl → ZnCl2 + H2

Apparatus used:

(a) Electrolysis of Water

(b) Steam Reforming

(a) Combustion

(b) Reducing Property

(c) Reaction with Non-metals

Activity Series (Simplified)

Examples:

1. Water (H₂O)

Properties:

Uses:

Uses:

Uses:

Test:

Uses:

SULPHUR AND ITS COMPOUNDS at a glance

Key Advantages

Simple Summary

Answer Key

Thursday, 16 April 2026

SOLUBILITY at a glance

Sample Solubility Data (g per 100 g of water)

How the Solubility Curves Look

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