IUPAC NOMENCLATURE at a glance

          IUPAC NOMENCLATURE

This is a systematic method of naming organic compounds using IUPAC system. That is, the International Union of Pure and Applied Chemistry.  

The IUPAC system of naming organic compounds, the following rules are to be followed.

Every organic compound has 2 or three parts to its name, 

**the root and the suffix or 

**the prefix, the root and thwe suffix  

Organic Compounds without branches or that does not have any subtituents apart from the main the main functional group will have only two parts to their name.

While those with branches will have three parts to their names.

***The ROOT: - This is got from the longest continuous carbon chain in the molecule. We use the Greek system of numbering to indicate the root as follows

Number of C-atom	Name
one C-atom	Meth-
two C-atoms	Eth-
Three C-atoms	Prop
Four C-atoms	But-
Five C-atom	Pent -
Six    C-atoms	Hex-
Seven C-atoms	Hept-
Eight C-atoms	Oct-
Nine   C-atoms	Non-
Ten     C-atoms	Dec-

*** The SUFIX: - This is usually added after the root hydrocarbon, it indicates the family or homologous series that the organic compound belongs to. 

***PREFIX / PREFIXES: - These are usually hanging atoms or groups that are not the main functional group of the compound. They are usually named before the root hydrocarbon. Their positions are usually mentioned (using arithmetic integers like 1,2,3,...)  before their names, and where you have more than one of the same types, we use mono -, di-, tri-, tetra- to indicate the number.  

when we have more than one functional group in a compound, then one is named as the prefix and the other the sufix. In this case we will not use the name as a suffix but as a prefix. (see functional groups)

RULE 1: Select the longest continuous carbon chain in the molecule and use it as the root or the parent hydrocarbon name of this chain.

RULE 2: Every branch off the main chain should be considered as a substituent derived from a corresponding hydrocarbon or any other hanging group that is not a hydrogen 

 CH₄ -methane      CH₃ –   methyl, 

C₂H₆-ethane         CH₃CH₂- ethyl, 

C₃H₈ - propane      C₃H₇ - propyl  

All of these functions as prefix

RULE 3: Number the carbon atoms of the continuous chain from a direction that gives the Carbon atom carrying the substituent ( i.e the Carbon atom carrying anything other than a H-atom will have a lower number) a small number

RULE 4: Give each substituent a name and number

RULE 5: For identical substituents, use di, tri, tetra, penta, hexa, and so on to indicate the number of identical substituents.

RULE 6: Where you have more than one substituent that are different, name them alphabetically

RULE 7: Give the lowest possible number to the functional group.

NOTE: Halogen when they occur in organic compounds are named thus, chlorine = chloro, fluorine = fluoro, bromine = bromo, iodine = iodo.

Always show your bonds when you write or draw structures of organic compounds 

 E.g .1 write the structure of 2-methyl butane. This should be written as shown below:

                       

H  H  H  H                 ׀   ׀   ׀    ׀            H-C-C-C-C-H                 ׀   ׀    ׀    ׀                H   ׀   H  H                 H-C-H                      ׀                     H

                         

Following strictly the above rules, one can then name perfectly any organic compound with ease. For example, in naming the compound below, following the rules

 

                                          CH₃ 
                                                    |                                                                         
                                 C¹H₃C²H₂C³H₂C⁴H₂C⁵H₂C⁶H₃
                                                    |
                                                    CH₃ 

In the above structure, there are six carbon atoms in the longest continuous chain. Therefore, the parent or the ROOT hydrocarbon has a name Hex (RULE 1). There are 2 methyl substituents derived from another hydrocarbons (RULE 2)

Counting the position of the substituents on the continuous root chain, they both stand on the 4^th carbon atom when counting from left to right, but when counting from right to left, they appear on the 3rd carbon atom, hence the lowest position of 3rd carbon atom is considered (RULE 3)

Since the two substituents are similar, they are named dimethyl (RULE 4), hence the two substituents have a number 3 and name 3 and so can be named as 3,3-dimethyl (RULE 5). When this is combined with the parent hydrocarbon (RULE 1), the name of the compound becomes 3,3-dimethylhexane.

Other examples with their names are shown below following the stated rules.

                       CH₃                                                             CH₃
(i)                    |                                                                   |
              C1H₃-C2-C3H₂-C4H-C5H₃              (ii)        C1H₃C2H₂C3H-C4HC5H2C6H₃      
                       |            |                                                             |
                      CH₃     CH₃                                                        CH₃                                       
            2,2,4-trimethylpentane                                 3,4-dimethylhexane

                               CH₂CH₃                                                 CH₃
                                      |                                                               |
(iii)       C1H₃C2H₂-C3-C4H₂C5H₃                   (iv)       C1H₃-C2-C3H₃
                                      |                                                               |
                               CH₂CH₃                                                 CH₃
             3,3-diethylpentane                              2,2-dimethylpropane
                                                                                   

                                                                                                           CH₃      CH₃
                                                                                                            |            |
(v)        CH₃CH₂CHCH₃                         (vi)       CH₃—C−CH2-CHCH₃
                     |                                                                    |
                    CH₃                                                              CH₃    
            2-methylbutane                                  2,2,4-trimethylpentane

(vii)      CH₃CH₂CH—CHCH₃                      (viii)     CH₃CH₂CHCH₃
                              ׀                                                          ׀       ׀               
                            CH₃  CH₃                                                    CH₃

             2,3-dimethylpentane                          2-methylbutane

                   

                       CH₃                                                                                    CH₃ 

(ix)       CH₃ − C −CH− CH2−CH2 CH2CH3                     (x)        CH₃CH₂CHCH₂CHCH₂CH₂CH₃ 

                     CH₃     CH₂CH₃                                                                               CH₂CH₃  

            2,2-dimethyl, 3-ethylheptane                                        5-ethyl, 3-methyloctane

                                                                                 Cl

(xi)       CH₃CH₂CHCH₃                         (xii)      CH₃-C-CH₂CH₃ 

                          Cl                                                     Cl

            2-chlorobutane                                   2,2-dichlorobutane

(xiii)     CH₃CH₂CHCH₂CHCH₃              (xiv)     CH₃CHCH₂CHCH₃  

                         Cl         Br                                          Cl        Cl

            2-bromo, 4-chlorohexane                   2,4-dichloropentane

                            Cl         Br                                                 Cl

(xv)      C1H₃CH₂-C-CH₂-C-CH₃              (xvi)     CH₃CHCH₂-C-CH₃  

                            Cl         Br                                       Cl         Cl

            2,2-dibromo, 4,4-dichlorohexane       2,2,4-trichloropentane

                        CH₃ H     H    CH₃                                                               CH₃  H      H    CH₃ 

(xvii)    CH₃ – C –  C –   C – C – CH₃                  (xviii)   CH₃ – C –   C –   C – C – CH₃    

                       CH₂ CH₂ CH₂ CH₂                                                  CH₂  CH₂ CH₂ CH₂

                       CH₃  CH₃ CH₃ CH₃                                                       CH₂  CH₃ CH₃ CH₂

            4,5-diethyl,3,3,6,6-tetramethyloctane                      CH₃                  CH₃

                                                                                    5,6-diethyl,4,4,7,7-tetramethyldecane

(xix)     CH₃ – CH₂ – CH – CH₃

                                    CH₂Cl

            1-chloro – 2-methylbutane

ALKANES

ALKANES 

The alkanes are a homologous series of saturated aliphatic hydrocarbons with a general molecular formula of CnH2n+2.  The are the only saturated hydrocarbons because they contain only single bonds. The are found mainly in petroleum. The carbon atoms in the alkanes exhibit sp³ hybridization. There is a gradual change in the physical properties of the members from the gaseous state (for the lighter members) to the liquid state and then the solid state for the heavier compounds.

The first ten members of the series are.

1.       methane          CH₄

2.       Ethane             C₂H₆

3.       Propane           C₃H₈

4.       Butane             C₄H₁₀

_5.         Pentane           C₅H₁₂

6.        Hexane           C₆H₁₄

7.        Heptane          C₇H₁₆

8.        Octane            C₈H₁₈

9.        Nonane           C₉H₂₀

10.     Decane            C₁₀H₂₂

Chemical properties 

The alkanes undergo only two reactions, combustion and substitution reactions

1. Combustion Reaction: - this is a general property for all hydrocarbons. The alkanes burn in air or oxygen to yield Carbon (iv) oxide and water.

    CH_4(g) + O_2(g) → CO_2(g) + H₂O_(g)

2. Substitution Reaction: - Substitution reaction is the only other reactions that the alkanes can undergo because they are saturated.

A Substitution reaction is a reaction where one element (atom) replaces one or more of the hydrogen atoms in an alkane molecule.

METHANE: - This is the first and the simplest member of the alkane family. It has a molecular formula of CH₄ and a structural formula of

 

              H
               ׀
       H − C − H
               ׀
              H

It is found naturally in swamps or swampy areas when vegetations and dead organic matter decompose. It is also one of the major components in natural gas

Laboratory Preparation 

Methane is prepared in the laboratory by the action of sodium ethanoate on soda- lime.  (soda-lime is sodium hydroxide that has been slaked with lime CaO).

Soda- lime is preferred to caustic soda because 

1. It is not Deliquescent and 

2. It does not attack glass.

                                       Laboratory Preparation of methane 

CH₃COONa(S) + NaOH(s) → Na₂CO_3(s) + CH_4(g)  

Physical properties 

i.  It is a colourless gas. 

ii. It is less dense than air.

iii. It is insoluble in water.

Chemical properties 

I. Combustion: - methane burns with a pale blue flame in air or oxygen

CH_4(g) + O_2(g) → CO_2(g) + H₂O_(l) 

2. Substitution reaction: - Methane combines with Chlorine to produce various products.

The reaction is faster in the presence of light (photochemical reaction) and it occurs in stages.

I. CH_4(g) + Cl_2(g) → CH₃Cl + HCl

                             Mono chloromethane

II. CH₃Cl + Cl_2(g) → CH₂Cl₂ + HCl

                             dichloromethane

III. CH₂Cl₂ + Cl_2(g) → CHCl₃ + HCl

                            trichloromethane

IV.  CHCl₃ + Cl_2(g) → CCl₄ + HCl

                             tetrachloromethane

Uses of Methane 

I. It is used mainly as fuel sometimes mixed with other fuels

2. It is used to make hydrogen

3. It is used to make carbon black

4. When refined it is can be used as a rocket fuel

OBJECTIVE QUESTIONS 

1. What is the IUPAC name of the compound with this structure 

         H     H    H     H
         |        |      |        |   
H— C — C — C — C — H
         |        |       |         | 
         H      |      H       H
                  | 
          H —C—H
                  | 
                 H 
a. 3-methylbutane

b. 3-methylpentane

c.2-methylbutane 

d.2-methylpropane 

2.  Which of the following compounds is the structural isomer of the compound above?

a. 2,2-dimethylpropane 

b. 2-ethylpropane

c. 1,2-methylbutane 

d. 2-methylpentane

3. the energy value of petrol can be determined by a 

a. bomb calorimeter

b. catalytic cracker

c. fractionating column

d. thermometer

4. C8H18 will undergo the following reactions except 

a.  Cracking 

b. Combustion 

c. Substitution

d. Addition

5. One of the products of pentane in excess air 

a. pentanol 

b. pentene

c. nitrogen (II) oxide 

d. carbon (IV) oxide 

6. The gas produced when a mixture of sodium propanoate and soda lime is heated is 

a. Methane.

b. Pentane

c.. Ethane

d. Butene

 

THEORY QUESTIONS 

1. Methane reacts with chlorine under certain conditions to produce tetrachloromethane 

i.). State the condition for the reaction 

ii). Name the type of reaction

iii). Give two uses of methane 

iv). Name one natural source of methane.

                                                                                           ANSWERS

                                                                                           1. C 

                                                                                           2.  A

NITROGEN AND ITS COMPOUNDS at a glance

NITROGEN

Nitrogen occurs mainly as a free element in the air/ atmosphere, about 78% by volume of the atmosphere. It also found in the combined state in many compounds such as ammonia, urea, proteins and trioxonitrates (V) salts. it does not exhibit allotropy and is a diatomic gas 

LABORATORY PREPARATION

From Air

It can be prepared from air by first passing air through caustic soda to remove CO₂ and then over heated copper turnings to remove and O₂ [ the oxygen can equally be removed by passing the air through alkaline pyrogallol]. The nitrogen obtained is not pure and is denser than air because it contains about 1% by volume of rare/ noble gases.

Pure nitrogen is obtained in the laboratory by any of the following method below:

1.  Thermal decomposition of ammonium dioxonitrate (III)

a.  NaNO_2(aq) + NH₄Cl_(aq) → NH₄NO_2(aq) +NaCl_(aq)

b. NH₄NO_2(aq) →2H₂O_(l) + N_2(g)              

2.       Thermal decomposition of ammonium heptaoxodichromate (VI)

                       (NH₄)₂Cr₂O_7(s) → Cr₂O_3(s) + 4H₂O_(l) + N_2(g)

3.       Oxidation of ammonia by hot Copper (II) oxide

                        2NH_3(g)+3CuO_(s) → 3Cu_(s) + 3H₂O_(g)+ N_2(g)

4.             Reduction of dinitrogen (I) oxide by red-hot copper.

N2O_(g) + Cu_(s) → CuO_(s) + N_2(g)

INDUSTRIAL PREPARATION

Industrially, nitrogen is obtained by fractional distillation of liquid air.  (see industrial preparation of Oxygen)

PHYSICAL PROPERTIES

1.         It is colourless gas.

2.          It is an odourless.

3.          It is a  tasteless

4.         Pure nitrogen is lighter than air.

5.         Slightly soluble in water

6.         Melting point -210⁰C and   boiling point is -196⁰C

CHEMICAL PROPERTIES

1.       It reacts with very electropositive metals to form nitrides

      3Mg_(s) + N_2(g) → Mg₃N_2(s)

2.       It reacts with non – metals like hydrogen and oxygen to form ammonia and oxides respectively.

     N_2(g)+ 3H_2(g) → 3NH_3(g)

                 N_2(g) + 2O_2(g) → 2N₂O_(g)

USES

1.       It is used industrial manufacture of ammonia.

2.       Liquid nitrogen is used as a cooling agent.

3.       It is used as preservative in packaged foods to prevent rancidity.

The stages in which nitrogen from the atmosphere is converted into soil nitrogen and back to atmospheric nitrogen is summarized below.

1.   Oxidation of atmospheric nitrogen:

N_2(g) + O_2(g) →2NO_(g)

2NO_(g) + O_2(g)→ 2NO_2(g)

4NO_(g)+O_2(g)+2H₂O_(l)→4HNO_2(q)

 4NO_(g)+O_2(g)+2H₂O_(l)→4HNO_3(aq)

2.   Action of nitrogen-fixing bacteria: 

3. Nitrification by nitrifying bacterial.

4. Denitrification by denitrifying bacteria 

COMPOUNDS OF NITROGEN

OXIDES OF NITROGEN

1. NITROGEN (I) OXIDE, N₂O

Nitrogen (I) oxide also known as laughing gas. (it can cause uncontrollable laughter when inhale).

LABORATORY PREPARATION

It is prepared in the lab by thermal decomposition of ammonium trioxonitrate (V). Ammonium trioxonitrate (V) can not heated directly because the reaction being highly exothermic and may become uncontrollable leading to an explosion. 

a.  KNO_3(s) + NH₄Cl_(s) → KCl_(s) + NH₄NO_3(s)

b  NH₄NO_3(s) → 2H₂O_(g) + N₂O_(g)

PHYSICAL PROPERTIES

1.    It is a colourless gas 

2.   It has faintly sickly sweet smell.

3.      It has a sweetish taste.

4.  It is fairly soluble in cold water.

6.   It is a neutral gas

CHEMICAL PROPERTIES

1.       It decomposes on strong heating to form nitrogen and oxygen.

      2N₂O_(g)→ O_2(g)+2N_2(g)

2.     It  burns in any  substance which is hot enough to decompose it.

    Mg_(s)+ N₂O_(g)→ MgO_(s)+ N_2(g)

3. it is reduced to nitrogen when in contact with very hot iron or copper. 

 Cu_(s) + N₂O_(g)→ N_2(g)+ CuO_(s)

TEST FOR N₂O

When a glowing splinter is inserted into the jar containing the unknown gas and it  rekindles, then the gas is either oxygen or nitrogen (I) oxide. If the gas has a pleasant smell and does not produce brown fumes of nitrogen (IV) oxide when burnt in air; then the gas is nitrogen (I) oxide.

USE: Nitrogen (I) oxide is used as anesthetic for minor surgical operations.

NITROGEN (II) OXIDE, NO

LABORATORY PREPARATION

Nitrogen (II) oxide is prepared by reacting combining copper with 50% trioxonitrate (IV) acid.

3Cu_(s) + 8HNO_3(aq)→ 3Cu(NO₃)_2(aq)+ 4H₂O_(l) + 2NO_(g)

 brown fumes of nitrogen (IV) oxide produced by some of the nitrogen (II) oxide as they react with oxygen is removed as the gas is pass through water.

PHYSICAL PROPERTIES

1. It is a colourless gas 

2. It is a poisonous gas.

3.  It is a sp7aringly soluble in water.

3.  It is slightly denser than air.

4.  It is neutral to litmus.

CHEMICAL PROPERTIES

1.  It combines readily with oxygen to form brown fumes of nitrogen (IV) oxide

         2NO_(g) + O_2(g) → 2NO_2(g)

2.   At high temperature, it decomposes to form equal volume of nitrogen and oxygen

         2NO_(s)→ N_2(g) + O_2(g)

3.   It is reduced to nitrogen by hot metals

 2Cu_(s)+ 2NO_(g) → 2CuO_(g) + N_2(g)

4.  It decolourizing acidified potassium tetraoxomanganate (VI) slowly ( reducing agent)

3MnO₄^-_(aq)+ 4H⁺_(aq) + NO_(g)→3Mn²⁺_(aq) 5NO₃^-

Test for NO

1. With acidified  iron (II) tetraoxosulphate (VI): A solution of acdified FeSO₄ is poured into the gas jar containing the unknown gas. If the solution turns dark brown, then the gas is NO.

NITROGEN (IV) OXIDE, NO₂

LABORATORY PREPARATION

It is prepared by thermal decomposition of lead (II) trioxonitrate (V) Pb(NO3)2. 

Pb(NO3)2 is preferred because it does not contain water of crystallization which can interfere with the preparation.

          

Dig

Pb(NO₃)_2(s) → 2PbO_(s) + O_2(g)+ 4NO_2(g)

The gaseous mixture obtained is passed through a U- tube dipped in ice, Nitrogen (IV) oxide liquefies as a green liquid (yellow if pure) in the tube while oxygen escapes out.

PHYSICAL PROPERTIES

1.  It is a reddish – brown gas.

2.  It has an irritating smell 

3. It  is a poisonous gas 

4.  It liquefies into yellow liquid at 21^oC.

5.  It is denser than air.

CHEMICAL PROPERTIES

1. It turns damp blue litmus paper red

2.  Nitrogen (IV) oxide exists mainly as dinitrogen (IV) oxide, N₂O₄ at low temperature. It decomposes on heating as follows.

N₂O_4(g) + 2O_2(g) → 2NO2_(g) + O_2(g)

•  Pale                    Reddish         
•  yellow                 brown                 

2.     It decomposes on heating to nitrogen and oxygen and so supports combustion 

  2NO_2(g) → N_2(g)+ 2O_2(g)

3.  With reducing agents it is reduced to nitrogen.

  4Cu_(s) + NO2 → 4CuO_(s) + N_2(g)

4.  With dissolved in water it forms two acids, dioxonitrate (III) and trioxonitrate (V) acids, hence, It is a mixed acid anhydride.

  H₂O_(l)+ 2NO_2(g) → HNO_2(aq)+ HNO_3(aq)

5.  It reacts with alkalis to form a mixture of dioxonitrate (III) and trioxonitrate (V) salts

  2KOH_(aq)+ 2NO_2(g) → KNO_3(aq) + KNO_2(aq) + H₂O_(l)

AMMONIA

Ammonia is a hydride of nitrogen. It is found in traces in the atmosphere from the decomposition/ decay of nitrogenous matter in the absence. Because is very soluble in water, it dissolves in rainwater and is washed down into the soil.     

LABORATORY PREPARATION OF AMMONIA

Ammonia is prepared in the laboratory by heating calcium hydroxide, Ca(OH)₂ (slaked lime) with ammonium chloride.

Ca(OH)_2(s)+ 2NH₄Cl_(s)→CaCl_2(s) +2H₂O_(l)+2NH_3(g).

It is dried using calcium oxide, CaO. Because it will react with drying agents like Conc. H₂SO₄ or fused CaCl₂, since it is an alkaline gas.

            

INDUSTRIAL PREPARATION

Ammonia is manufactured by the Haber process from nitrogen and hydrogen. In this process  nitrogen and hydrogen are reacted  in ratio 1:3 by volume. The reaction is reversible. The conditions for optimum yield of ammonia are 

i. A temperature of 450^Oc 

ii. A pressure of about 200atm and 

iii. Finely divided iron catalyst   

N_2(g) +3H_2(g) →2NH_3(g) + heat

PHYSICAL PROPERTIES

i.   It is a colorless gas 

ii. It has  a characteristic choking/ pungent smell.

iii. When inhaled in large quantity it is poisonous 

3. It is the only known alkaline gas.

4. It is about less dense than air.

CHEMICAL PROPERTIES

1. Ammonia burns readily in oxygen to yield and nitrogen and water vapour 

 4NH_3(g)+3O_2(g)→6H₂O_(g)+ 2N_2(g)

2. As a reducing agent, it reduces most metallic oxides to their metals. 

 i. 3CuO_(s) + 2NH_3(g) → 3Cu_(s) + 3H₂O_(l) + N_2(g)

ii.   With Chlorine it yields NH4Cl

  3Cl_2(g) + 8NH_3(g) → 6NH₄Cl_(s) + N_2(g)

3.  Ammonia reacts with carbon IV oxide to form Urea and water vapour.

 2NH_3(g)+ CO_2(g) → (NH₂)₂CO_(s) + H₂O_(l)

                        ^urea

4. With acids it form ammoniums salts.  

 2NH_3(g) + H₂SO_4(g)→(NH₄)₂SO_4(s)

TEST FOR AMMONIA

Ammonia has a choking and a pungent smell. It can be confirmed using:

1. Litmus paper: It turns damp red litmus paper blue

2.  Hydrochloric acid: it forms dense white fumes with a concentrated on a glass rod 

USES OF AMMONIA

1.  Is is one of the raw materials in the Solvay process for the   manufacture trioxonitrate (V) acid and Sodium trioxocarbonate (IV).

2. Liquid ammonia is used as a refrigerant.

3. Aqueous ammonia is used in softening temporary hard water.

4.    Aqueous ammonia is also used in laundries as a solvent for removing grease and oil stains.

TRIOXONITRATE (V) ACID, HNO₃

LABORATORY PREPARATION

Trioxonitrate (V) acid is a volatile acid. It is prepared in the laboratory by  displacement of the HNO3 from any trioxonitrate salt by concentrated H₂SO₄ which is less volatile. Trioxonitrate (V) of potassium or sodium is usually used because they are cheap.

KNO_3(s)+ H₂SO_4(aq)→ KHSO_4(aq)+HNO_3(aq)

NOTE: we use an  all-glass apparatus for this preparation because the hydrogen trioxonitrate (V) acid vapour will attack cork or rubber.

INDUSTRIAL PREPARATION

It is prepared by the catalytic oxidation of ammonia:

-    Ammonia is treated with excess air using Platinum-rhodium catalyst at 700^oC to produce

4NH_3(g)+ 5O_2(g)→ 4NO_(g)+ 6H2O the nitrogen (II) oxide formed is cooled and mixed with excess air to produce nitrogen (IV) oxide.

2NO_(g) + O_2(g) →2NO₂(g)

-    Nitrogen (IV) oxide formed is dissolved with excess air in hot water to yield trioxonitrate (V) acid solution of up to 50% concentration. 

4NO_2(g)+ 2H₂O_(l)+ O_2(g) → 4HNO_3(aq)

PHYSICAL PROPERTIES

1.  Pure HNO3 acid is a colourless liquid with sharp choking smell. It fumes in air. The acid decomposes to give NO2 gas which redissolves in the acid turning it yellow after a while.

2. The density of the pure acid is 1.52 gcm^-3

3.  The pure acid boils at 86⁰C and melts at -47^oC  

4.   The pure acid dissolves in water in all proportions 

5.  The concentrated form of the acid is corrosive.

CHEMICAL PROPERTIES

1.  As an acid 

I. The dilute acid turns blue litmus red.

 ii.  it neutralizes bases and alkalis to form metallic trioxonitrate (V) and water only

NaOH_(aq)+HNO_3(aq) → NaNO_3(aq)+ H₂O_(l)

iii. it reacts with trioxocarbonate (IV) to liberate carbon (II) oxide 

 CaCO_3(s) + HNO_3(aq) → Ca(NO₃)_2(aq)+ H₂O_(l)+ CO_2(g)

3.  Unlike other acids, it rarely gives out hydrogen with metals except when very dilute solution is reacted with Ca, Mg or Mn.

4.    As an oxidizing agent, 

it oxidizes non–metal like Sulphur to form the corresponding oxides of the non – metals.

  S_(s)+ 6HNO_3(aq)→H₂SO_4(aq) + 2H₂O_(l) + 6NO_2(g)

ii.   it oxidizes least reactive metals like Cu, Pb, Hg and Ag to yield the respective trioxonitrate (V) and nitrogen (IV) oxide.  With moderate  concentration  it yields nitrogen (II) oxide.

Aluminum and iron are not oxidized by the acid, because of the  formation of a thin  coating of the oxide on the surface of the metal which is lmpervious to further attack on the metals. 

Hence, containers lined with aluminum and iron can be used to transport concentrated HNO_3(aq)

5.As an oxidizing agent, it oxidizes hydrogen sulphide to sulphur

  H₂S_(g) + 2HNO_3(aq) → S_(s)+ 2H₂O_(l)+2NO_2(g)

6.  it oxidizes iron (II) salts to iron (III) salts

 6Fe²⁺_(aq) + 8H⁺_(aq) + 2NO₃^-_(aq) →   6Fe³⁺_(aq) + 4H₂O_(l) + 2NO_(g)

USES

1.  It is used as an acid, oxidizing agent and nitrating agent in the laboratory.

2. It is as rocket fuel

3. It is used in producing nylon and Terylene.

4.  It is used to produce fertilizers, dyes, drugs and explosives.

OBJECTIVE QUESTIONS 

1.  In which group of the periodic table is nitrogen found? 

(a) 2

 (b) 5 

(c) 7

(d) 6

2. The boiling point of nitrogen in ⁰C is

 (a) -183

 (b) -196

 (c) 200

 (d) 240

3.   The percentage of nitrogen in air is

 (a) 78 

(b) 75 

(c) 71

 (d) 67

4. The following are uses of nitrogen except a. as a cooling agent b. to prevent rancidity c. in the manufacture of fertilizers d. in laundry.

5. The atomicity of nitrogen is 

(a) 1

(b) 2

 (c) 3

 (d) 4

6.  Which of the following compound will leave a metal residue when heated 

a. Cu(NO₃)₂

b. AgNO₃

c. K₂CO₃

4.CaCO₃

7.  The gas given off when NH4Cl is heated with an alkali is 

a. H₂

b. Cl₂

c. N₂ 

d. NH₃

8. 

9. 

10.

11. 

12.

THEORY

 

1a.   State TWO physical properties and TWO chemical properties of nitrogen.

1b   Mention THREE uses of nitrogen.

1c(i) Briefly describe the preparation of nitrogen from air in the laboratory. 

2a(i)   Give an equation to show the laboratory preparation of nitrogen (II) oxide.

2b. Describe a test to distinguish between nitrogen (I) oxide and oxygen gas.                    

2c(iii) Briefly describe the laboratory preparation of ammonia.

3a   State TWO physical and THREE chemical properties each of ammonia.                                       

3b.  Describe the laboratory preparation of trioxonitrate (V) acid.

3c  Write TWO equations of reactions in which trioxonitrate (V) is acting as an acid.

4a. Write an equation to show the reaction of nitrogen (IV) oxide as a mixed anhydride.

4b.  Describe the electrolysis of CuSO₄ solution using platinum electrodes.

4c. Classify the following oxides: CuO, Na₂O, PbO, NO₂, N₂O

ELEMENTS, MIXTURES and COMPOUNDS at a glance

 

ELEMENTS: - An element is a substance that cannot be split into simpler units by any ordinary chemical process. 

examples of elements include sodium, oxygen, carbon, nitrogen e.t.c.

There about 118 elements that has been discovered so far and grouped into metals and non-metals in general. we also have elements that are referred to as metalloids, these are actually nonmetals that show or exhibit some metallic properties.

Examples of metals and non-metals 

Metals                 Non-metals

Sodium                Oxygen

Potassium           Carbon

Iron                     Silicon

Gold                    Lead

Tin                      Sulphur 

Calcium              Phosphorus 

 

METALS: - These are elements that ionize by the loss of electrons.

Na → Na⁺ + e^-

Ca → Ca²⁺ + 2e^-

Al → Al³⁺ + 3e^-

They form positively charged ions, that is, Cations when the loss electrons (ionize)

Physical Properties of Metals

i.  Metals are malleable, that is they can be beaten or hammered into flat sheets. 

ii. Metals are ductile, that is, they can be drawn into wires

iii. Metals are Sonorous, i.e. they produce musical notes when struck

iv. Metals conduct heat and electricity

v. Metals have metallic luster, i.e.  they shine when polished.

vi. metals have high tensile strength

Chemical Properties of Metals 

i. Ionization: - Metals ionize by the loss of their valence (outermost) electrons to form Cations

Na_(s) → Na⁺ + e^-

Mg_(s) → Mg²⁺ + 2e^-

Al_(s) → Al³⁺ + 3e^-

ii. Reaction with air: - most metals especially the group I metals like sodium, potassium when exposed to air reacts with the atmospheric gases and become tarnished. Example 

4Na_(s) +O_2(g) → 2Na₂O_(s)

Na₂O_(s) + H₂O_(l) → 2NaOH_(aq)

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

iii. Reaction with Acids: - Most metals react with dilute acids to liberate hydrogen gas. Example

I. Mg_(s) + H₂SO₄ → MgSO_4(aq) + H_2(g)

ii. Ca_(s) + 2HCl_(aq) → CaCl_2(aq) + H_2(g)

Reaction with Bases: - Some metals react with Bases to form complex salts. These metals are said to be Amphoteric elements. Examples include Aluminium (Al), Tin (Sn), Zinc (Zn) and Lead (Pb).

Zn_(s) + 2NaOH_(aq) + 2H₂O_(l) → Na₂Zn(OH)_4(aq)

Reaction with non-metals: - Most metals combine directly with nonmetals to form compounds, example metals combine with oxygen to form oxides, with sulphur to form sulphides, with nitrogen to form nitrides.

   Ca_(s) + O_2(g) → CaO_(s)

   Fe_(s) + S_(s) → FeS_(s)

    2 Mg_(s) + O_2(g) →MgO_(s)

 

NON-METALS: - These are elements that ionize by gaining electrons.

They form negatively charged ions known as Anions, when they gain electrons

Example

Physical properties of nonmetals 

i. Non-metals do not conduct heat and electricity

ii. They are hard and brittle i.e. they break easily  

iii. They have low tensile strength 

iv. They do not shine when polished

v. They are not malleable 

vi. They are not ductile 

COMPOUNDS: - A compound is a substance formed when two or more elements are chemically combined together.

examples of compounds include

 i. sodium chloride (NaCl), 

ii. calcium trioxocarbonate (IV) (CaCO₃),

Iii. Water (H₂O)

Iv. Sugar (C₆H₁₂O₆)

MIXTURES: - Mixtures are substances that contain two or constituents that can be separated by physical methods.    

                 Differences between Compounds and Mixture 

	Compounds	Mixture
i.	Can be represented by a formula	Can not be represented by a formula
ii	Is always homogenous (every part of the compound is always the same)	May be homogenous (that is, every part of the mixture is the same) or heterogenous (every part of the mixture is not the same)
iii.	Composition is always constant	Composition is not constant
iv.	Property is different from the properties of the individual elements that make up the compound	Constituents still retain their individual properties
v.	The elements are chemically combined together	The constituents are not chemically combined

 

Example of mixtures include: - 

	Mixtures	Constituents
i.	Sodium chloride solution	Sodium chloride + water
ii.	Blood	Plasma + red and white blood cells
iii.	Urine	Water + salts + Urea
iv.
v.
vi

               

In order for substances to be analyzed they have to be separated into their pure forms

SEPARATING TECHNIQUES at a glance

 

TOPIC: STANDARD SEPARATION TECHNIQUE

STANDARD SEPARATION TECHNIQUES
These are the various methods that are available and used to separate components of a mixture from the mixture. they include the following methods discuused below

1. SIEVING

This is used to separate solid particles of different sizes. Particles smaller than the size of the sieve (mesh) pass through leaving behind particles of larger sizes. It is used in gold and diamond mines and in garri industries.

2. MAGNETIC SEPARATION

This method is used to separate magnetic substances from non-magnetic particles. It makes use of a magnet. An example is the separation of a mixture of iron filings  or pins and sugar.

It is used in mining and steel industries. It can be used to remove magnetic impurities from tin ores. It can be used to separate iron filings from sulphur powder.

3. FILTRATION

Filtration is a separation technique that involves separating an insoluble solid from a liquid using a filter. For example, a mixture of chalk particles in water can be separated using filtration technique. 

Filtration is used in industries such as water purification plants and breweries

                                                      fig.1 filtration of muddy water

4. CENTRIFUGATION:

Centrifugation is a standard separation technique used to separate a mixture of insoluble solid from liquid by using a centrifuge. A centrifuge is a machine which can spin test tubes containing suspensions at high speed. Centrifugation is often used when there is only a small amount of material. In hospitals, blood samples are centrifuged to separate the blood cells from the plasma.                                        

5. DECANTATION

Decantation is a separation technique used to separate a mixture containing insoluble solid from a liquid. This is done when the mixture is allowed to settle down with the upper clear liquid carefully poured or decanted into a clean container thereby leaving the lower solid in the container originally containing the mixture. This is a quick but inaccurate method of separating the components of a mixture.

6. EVAPORATION

Evaporation is a separation technique used to recover soluble solute from its solvent. For example, salt can be separated from salt solution by evaporation.

fig.3. Evaporation of a salt solution0

Evaporation is used in salt –making industries.

7. CRYSTALLIZATION

Crystallization is used to obtain pure crystals of salts which decompose easily on heating, from its solution. 

The solution is concentrated by heating until it is concentrated, and it is then allowed to cool down, the crystals start to form as the solution cools down. To induce crystal formation:

(i). some crystals of the salt are added (seedling)

(ii). use a glass rod to scratch the inside of the container.  

Crystallization is used in drug industries and sugar industries, industries where purity of a substance is important.

8. FRACTIONAL CRYSTALLIZATION

It is used to separate two or more solutes (solids) which are present in the same solution. The solutes to be separated must have different solubilities at different temperatures. Starting from a particular temperature, as cooling of the solution begins the solutes that is least soluble begins to appear, that is, the crystals that are least soluble at that particular temperature begins to crystalize out leaving the more soluble salts in the solution.

9. PRECIPITATION

In precipitation, a difference in the solubility of a solid in two different miscible liquids is used. For example, FeS0₄ is soluble in water but not on ethanol. If ethanol is added to a solution of FeS0₄ in water, the FeS0₄ will be precipitated out of the solution and filtered out.

10. SUBLIMATION

Sublimation is the change of state from solid to gas directly on application of heat. Examples of substances that sublime are iodine and ammonium chloride. Sublimation can be used to separate these substances. The pure crystal recovered is the sublimate.

    Fig. 

 

11. DISTILLATION

              

This method is used to recover a solvent from a solution. It involves heating the liquid until it vapourizes and then condensing the vapour with the aid of a condenser into a liquid called distillate. The solute and other impurities remain in the distillation flask. This method is used in gin/brandy and water distilleries to manufacture gin and distilled water.

FRACTIONAL DISTILLATION

This method is used to separate a mixture of two or more miscible liquids with close boiling points. When two liquids have boiling points that are very close (less than 10^oC ) it becomes difficult to use simple distillation. A fractionating column is inserted into the distillation flask.the fractionating column does the actual separation

How the fractionating column works: - As the mixture boils and enters the fractionating column, the vapours loss their heat to the glass beads in the fractionating column and falls back into the mixture, (i.e by returning components whose boiling point is less than that of the fractionating column). Only components whose boiling point is the same as the fractionating column are allowed to pass into the condenser. This method is used in the refinery to separate crude oil into its various fractions, also the extraction of oxygen and nitrogen from Liquified air, the manufacture of ethanol and to separate benzene and methyl benzene mixture.           

SEPARATING FUNNEL

This method is used to separate a mixture of two immiscible liquids or a polar liquid from a non-polar liquid. It depends on the densities of the two liquids. The less dense liquid will float on top and the denser below. It is used to separate water and kerosene

Diag.  Separation of a mixture of kerosene and water.

CHROMATOGRAPHY

This method uses a solvent moving over an adsorbent medium (paper) which is porous to separate mixtures of solutes.

                 

A chemist uses liquid chromatography to analyze a complex mixture of substances. The chromatograph utilizes an adsorptive medium, which when placed in contact with a sample, adsorbs the various constituents of the sample at different rates. In this manner, the components of a mixture are separated. Chromatography has many valuable applications, such as determining the level of pollutants in air, analyzing drugs, and testing blood and urine samples.

Types

1.            Paper chromatography

2.            Thin layer chromatography

3.            Gas chromatography

4.            Column chromatography

In paper chromatography, a solution, such as ink, is spotted into the paper (stationary phase) near one end. The paper is then dipped into an appropriate solvent such as water or ethanol (mobile phase) in a closed air-tight jar. The solvent moves up the paper and separates the substance into various spots.The paper is removed and dried. The different spots on the paper show the different constituents the substance (ink, dye or chlorophyl) contains.

USES

i). It is used in medicine to analyze blood.

ii). It is used in the industry to identify petroleum fractions.

iii). It is used in scientific research.

CRITERIA FOR PURITY

1.            The melting point and boiling point of a pure substance are fixed but change in the presence of impurities. Impurities lower the melting point of a substance and increase its boiling point.     

And the criteria for purity is 

1. Sharp melting point: substance must melt at a specific temperature 

2. Sharp boiling point: substance must boil at a specific temperature called the boiling point.

3. Substance must have a constant density 

4. Substance must show only one spot on a chromatographic plate.

GENERAL EVALUATION

1.            Explain the following separation techniques. Magnetic separation, paper chromatography and sieving

2.            Describe how you would separate a mixture of NaCl, PbCl₂ and NH₄Cl

3.            What method can be applied to separate a mixture of iron filings and sulphur

4.            Mention two criteria for purity of a substance.

 

OBJECTIVE QUESTIONS

1.  A mixture of oil and water can be separated by 

(a) sublimation

 (b) evaporation to dryness 

(c) using a separating funnel

 (d) fractional distillation

2.  Fractional distillation is used to separate

(a) an insoluble substance from a soluble volatile substance 

(b) liquids with differing boiling points

 (c) gas, liquid or solid impurities from a mixture 

(d) liquid with close boiling points

3. Which of the following separating techniques can be used to separate a mixture of iodine and sodium chloride? 

(a) distillation 

(b) evaporation  

(c) sublimation  

(d) decantation

4.  Which of the following is not a type of chromatography?

(a) thin layer 

(b) gas  

(c) paper 

(d) glass

5. Which of the following is a quick but inaccurate way of separating mixture?

 (a) decantation 

(b) evaporation  

(c) filtration  

(d) distillation 

6. How can you separate a mixture of iron filings and sulphur powder?

 (a) distillation 

(b) chromatography 

(c) magnetization  

(d) evaporation

7.  A mixture of calcium chloride and calcium trioxocarbonate (IV) in water can be separated by

(a)Evaporation

(b) Sublimation

(c) Distillation

(d) Filtration

8.  CuSO4.5H2O can be obtained from an aqueous solution of copper (II) tetraoxosulphate (VI) by

(a) evaporation to dryness

(b) Using chromatography

(c) precipitation

(d) crystallization.

9. Which of these separation technique can be used to separate an insoluble solid from a liquid

(a) centrifugation

(b) chromatography

(c) distillation

(d) sublimation

10. Which of these techniques would you use to obtain pure water from sea water?

(a) chromatography

(b) crystallisation

(c) distillation

(d) filtration

11. Ethanol is a product of fermentation of simple sugars. Which method is used to separate ethanol from other products?

(a) boiling off the ethanol

(b) filtration

(c) precipitation

(d) fractional distillation

12.  A spot of oil paint on a shirt can best be removed using

(a) brine.

(b) detergent

(c) kerosene

(d) warm water.

13. Which of these techniques would you use to separate a mixture of ammonium chloride and sodium chloride

(a) centrifugation

(b) chromatography

(c) distillation

(d) sublimation

14. Which of the following is not a separation technique?

(a) Crystallization

(b) Distillation

(c) Evaporation

(d) Hydration

15. Fractional distillation of petroleum depends on differences in

(a) boiling points

(b) densities

(c) freezing points

(d) solubilities

16. Pure solvents are obtained by

(a) evaporation

(b) extraction

(c) condensation

(d) distillation

17.  The constituents of leaf pigment can be separated by

 (a) chromatography

(b) filtration

(c) fractional crystallization

(d) fractional distillation

18. The separation of Oxygen from nitrogen by fractional distillation of air is possible because 

a). nitrogen is less dense than oxygen

b). oxygen is more reactive than nitrogen

c). of the difference in their boiling points.

d). they belong to the same period. 

19. The purity of a solid sample can best be determined by its 

a). boiling point

b). melting point 

c). conductivity.

d). solubility.

20. 

    THEORY

1.(a) The diagrams labelled I to IV below illustrate different laboratory set-ups used in the separation of mixtures. 

i). Name the separation technique illustrated by each diagram 

ii). Which of the set-ups is used for concentrating dilute salt solutions, for the purpose of                 crystallization  

iii). Which of the set-ups is used inobtaining pure water from muddy water?

iv). Mention the set-up you would use to separate a polar solvent from a non-polar solvent 

v). State the modification you would make to the set-up labelled IV in order to use it for separating a mixture of NaCl and NH4Cl [waec]

2. (a)i. Mention two criteria for purity of a substance.

PARTICULATE NATURE OF MATTER

TOPIC: PARTICULATE NATURE OF MATTER

CONTENT

- ATOMS AND MOLECULES

- IONS

- DALTON’S ATOMIC THEORY

- MODIFICATIONS OF DALTONS ATOMIC THEORY

ATOMS AND MOLECULES

Matter is made up of discrete particles. The main ones are atoms, molecules, and ions.

An atom is the smallest part of an element which can take part in a chemical reaction.

A molecule is the smallest particle of a substance that can exist alone and still retains the chemical properties of that substance. 

Molecules are made up of atoms. These atoms may be the same or may be different

ATOMICITY: - This is the number of atoms in one molecule of an element or a compound

We have monatomic, diatomic and triatomic for those elements that contain one atom, two atoms and three atoms respectively in their molecules.

Examples:

Element            Atomicity

Neon                Monoatomic    Ne

Helium            Monoatomic    He

Argon              Monoatomic    Ar

Hydrogen        Diatomic         H2

Oxygen           Diatomic          O2

Nitrogen         Diatomic          N2

Ozone             Triatomic        O3

Sulphur           Polyatomic      S8

Water               triatomic          H2O   

Limestone        pentatomic      CaCO3

IONS

An ion is an atom or group of atoms which carries an electric charge. They are formed when atoms loss or gain electrons. 

Generally, ions are grouped as cations and anions. 

Cations are positively charged ions e.g. Ca²⁺, Na⁺, NH₄⁺ etc.

Anions are negatively charged ions e.g. C0₃^2-, S0₄^2-, Cl^-, OH^-, etc.

We also have group of atoms that carry a single charge, whether positive or negative charge, they are called RADICALS.

An acid radical is thus a small group of atoms carrying a negative charge that keeps, 

Examples include S0₄^2-, N0₃^- e.t.c

DALTON’S ATOMIC THEORY

John Dalton, a British Physicist and Chemist (1808) proposed the atomic theory thus: 

1.            All elements are made up of small indivisible particles called atoms.

2.            Atoms can neither be created nor destroyed in any chemical reaction.

3.            Atoms of a particular element are exactly alike in all aspect and are different from atoms of all other elements.

4.            Atoms of different elements combine in simple whole number ratios to form compounds.

5.            All chemical changes result from the combination or separation of atoms

MODIFICATIONS OF DALTON’S ATOMIC THEORY

Due to new discoveries in the twentieth century, Dalton’s atomic theory cannot hold in its totality.  setting new modifications have been made There is need for its modification.

i.  Due to the discovery of the sub-atomic particles, (protons and electrons) the atom is no longer believed to be indivisible.

ii. Due to the discovery of radioactivity and radioisotopes which involves the destruction of atoms and formation of new elements during nuclear reactions, the atom is no longer believed to be indestructible. however. This second statement still holds good for ordinary chemical reactions

iii.  Due to the discovery of isotopes and isotopy, the third statement is no longer acceptable. 

iv.  Due to the discovery of very large organic molecules such as proteins, starch and fats which contain thousands of atoms. The fourth statement is no longer true for organic compounds but still remains true for inorganic compounds which contain a few atoms per molecule.

Objective Questions

1. Which of the following is not a constituent of the atom

 (a) proton  

(b) electron

 (c) neutron

 (d) isotope

2. Which of the following statement about an atom is not correct?

 (a) it is indivisible

(b) it is destructible in some cases 

(c) it is the smallest part of a substance that takes part in a reaction 

(d) it is made up of protons, neutrons and electrons

3.  Which of the following is a liquid at room temperature? 

(a) copper (b) gold  (c) mercury

 (d) silver

4.   What is the atomicity of neon? (a) monoatomic (b) diatomic (c) triatomic  (d) polyatomic

THEORY

1.(a)i  State any two postulates of the Dalton’s atomic theory.

ii. state the modification of the postulates mentioned above

2.(a)i. Differentiate an atom from a molecule.

ii. How will an atom become an ion?

1.  Define an atom.

2.  Give two examples of diatomic molecules.

EVALUATION

1. What are ions?
2. State the cation and anion present in (I) H₂S0₄   (ii) NaCl (iii) FeS0₄