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.

2. 

(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^-