GRADE 10- CHEMISTRY NOTES FROM PG 66-76
HOMOLOGOUS SERIES
A series of compounds in which the same functional group substitutes for hydrogen in a carbon chain is called a
homologous series.
Characteristics of homologous series
1.
2.
3.
All members of the series differ by a –CH2 unit.
The molecular mass of the succeeding members differ by 14 amu.
The different members show regular gradation in their physical properties.,
Eg. Mp, BP etc
4. Different members of the series show similar chemical properties
5. They can be represented by a general formula.
CHEMICAL PROPERTIES OF CARBON COMPOUNDS
1. Combustion
Burning of carbon compounds in air produces CO2, H2O and energy in the form of heat and light
I)
C + O2  CO2 + heat and light
II)
2CH4 + 4 O2 2 CO2 + 4 H2O + heat and light
III)
C2H5OH + O2  CO2 + H2O + heat and light.
Saturated hydrocarbon
less reactive
they are with single bonds
between the carbon atoms
In a chain (alkanes)
Combustion - burn with a blue, nonsooty
Flame
Reactivity Structure -
unsaturated hydrocarbon
very reactive
they have double/triple
bonds between the carbon atoms
such as in alkenes and alkynes
burn with a yellow sooty flame due to
higher % of carbon in them and thus undergo
Incomplete combustion.
2.
Oxidation
Ethanol is oxidized by alkaline potassium permanganate or acidified potassium dichromate
(oxidizing agents) to produce ethanoic acid. (write the activity 4.5 on pg 70)
C2H5OH (-alk KMnO4+heat-)-----------/(aci,K2Cr2O7+heat-)------------- CH3COOH
3.
Addition Reaction
Unsaturated hydrocarbons undergo addition reactions in which a molecule of a substance is added across a
double or a triple bond eg unsaturated hydrocarbons add hydrogen in the presence of a nickel catalyst to
give saturated hydrocarbons.
C2H4
---(Nickel catalyst)/ H2-------- C2H6
Application of hydrogenation—It is used to convert vegetable oils to vanaspati in the presence of
Nickel catalyst.
4.
Substitution reaction.
Saturated hydrocarbons undergo substitution reaction with chlorine in the presence of sunlight .
In this reaction, chlorine replaces the hydrogen atom one by one.
CH4 + Cl2 --- (sunlight)- CH3Cl + HCl
CH3Cl……..CH2Cl2……CHCl3….CCl4
CARBON COMPOUNDS
ETHANOL ---C2H5OH (Ethyl alcohol)
Properties.
1.active ingredients of all alcoholic drinks.
2.being a good solvent , it is used in medicines suchas tincture iodine ,cough syrups.
3.pure ethanol is called absolute alcohol.
REACTIONS
1.WITH SODIUM METAL
Ethanol reacts with sodium metal liberating hydrogen gas.
2C2H5OH
+ 2Na - 2C2H5ONa + H2
2. DEHYDRATION REACTION
Ethanol, on heating with hot conc.sulphuric acid, results in dehydration of ethanol
and forms ethene.
C2H5OH
--conc.H2SO4(at 443K)---------- C2H4 + H2O
(here, sulphuric acid acts as a dehydrating agent)
ETHANOIC ACID –CH3COOH (acetic acid)
Properties
1 .Vinegar is 5-8% solution of aceticacid in water which is used as preservative in pickles.
2. It freezes during winter to form ice like solid called glacial acetic acid.
3. The melting point of pure ethanoic cid is 290K
1.. ESTERIFICATION REACTION
ACTIVITY—take 1ml of ehanol and 1ml of ethanoic acid in a test tube .Add few drops of
Conc.H2SO4 and warm in a water-bath for five minutes. Pour the content into abeaker
Containing 20-50ml of water. Smell the resulting mixture.
CH3COOH + C2H5OH-----(conc.H2SO4)- CH3COOC2H5 + H2O
Ethyl acetate-(ester)
Esters are sweet smelling substances. These are used in making perfumes and flavouring agents.
. SAPONIFICATION REACTION
Alkaline hydrolysis of esters produces soaps.
CH3COOC2H5 + NaOH - CH3COONa + C2H5OH
2. Reaction with a base
Ethanoic acid on reacting with a base eg NaOH, Sodium ethnoate (sodium acetate ) Is formed.
CH3COOH + NaOH -- CH3COONa + H2O
3.Reaction with carbonates and hydrogencarbonates.
CH3COOH + Na2CO3 - 2CH3COONa + H2O +CO2
CH3COOH + NaHCO3  CH3COONa + H2O +CO2
CLEANSING ACTION OF SOAP
QUESTIONS AND ANSWERS
Q. Explain the cleansing action of soap.
Refer the text.
Q What is soap?
A soap is the sodium salt of a long chain carboxylic acid which has cleansing properties in water.
Eg. Sodium stearate C17H35COONa
Sodium palmitate C15H31COONa
FAT or OIL + NaOH 
SOAP + GLYCEROL
Q. Name two synthetic detergents
1. Sodium n-dodecyl benzene sulphonate
2. Sodium n-dodecyl sulphate
Q. Differentiate between soaps and synthetic detergents.
SOAPS
Soaps are the sodium salts of
ththlong ch the long chain carboxylic acid
………………...The ionic group in soap is –
COO Na
Soaps do not form lather in
hard water
Soaps are prepared from
vegetable oil or animal fat
Soaps are biodegradable.
Soaps have relatively weak
cleansing action
SYNTHETIC DETERGENTS
Synthetic detergents are the sodium
salts of long chain benzene sulphonic
acid or long chain alkyl hydrogen
sulphates. The ionic group in this is
-SO3-Na+ or –SO4-Na
Detergents can be used for washing
even when the water is hard
They are prepared from
hydrocarbons of petroleum.
Not biodegradable
Synthetic detergents have a strong
cleansing action.