"AKC SCIENCE CLASSES"
CLASS 10 TH (CBSE AND MP BOARD)
CHAPTER 04
CARBON AND ITS COMPOUNDS
EXERCISES QUESTIONS AND ANSWERS
Q.01:- Ethane, with the molecular formula C2H6 has :-
(a) 6 covalent bonds
(b) 7 covalent bonds
(c) 8 covalent bonds
(d) 9 covalent bonds
Ans:- (b) 7 covalent bonds
Q.02:- Butanone is a four-carbon compound with the functional group:-
(a) Carboxylic acid
(b) Aldehyde
(c) Ketone
(d) Alcohol
Ans:- (c) Ketone
Q.03:- While cooking, if the bottom of the vessel is getting blackened on the outside, it means that :
(a) the food is not cooked completely
(b) the fuel is not burning completely
(c) the fuel is wet
(d) the fuel is burning completely.
Ans:- (b) the fuel is not burning completely.
Q.04:- Explain the nature of the covalent bond using the bond formation in CH3Cl.
Ans:- Covalent bonds is formed by sharing of electrons so that the combining atoms complete their outermost shell. In CH3Cl, this happens as follows:-
Q.05:- Draw the electron dot structures for
(a) Ethanoic acid
(b) H2S
(c) Propane
(d) F2
Ans:-
Q.06:- What is a homologous series? Explain with an example.
Ans:- A homologous series is a group of compounds which contains the same functional group but different chain lengths. Thus, these have the same chemical properties but different physical properties.
Examples :- CH3OH, C2H5OH, C3H7OH, C4H9OH are members of the same homologous series.
Q.07:- How can ethanol and ethanoic acid be differentiated on the basis of their physical and chemical properties?
Ans:-
| SL No. | Test | Ethanol | Ethanoic acid |
|---|---|---|---|
| 1 | Litmus test | No change in color of litmus solution. | Blue litmus solution turns red. |
| 2 | Sodium bicarbonate | No brisk effervescence. | Brisk effervescence due to evolution of CO2. |
| 3 | Sodium metal test | H2 is given out with effervescence | H2 is produced but no effervescence. |
Q.08:- Why does micelle formation take place when soap is added to water? Will a micelle be formed in other solvents such as ethanol also?
Ans:- The molecules of soap are sodium or potassium salts of long-chain carboxylic acids. The acid end of a soap dissolves in water while the carbon chain dissolves in oil when soap is added to water, the hydrophilic (acid end) will align along the surface of water and the hydrophobic tail (carbon chain) remains out of water. This cluster of molecules in which hydrophobic tails are in the interior of cluster is called micelle. Such micelle formation will not be possible in other solvents like ethanol in which sodium salt of fatty acids do not dissolve.
Q.09:- Why are carbon and its compounds used as fuels for most applications?
Ans:- Carbon and its compounds give a large amount of heat per unit weight and are therefore, used as fuels for most purposes.
Q.10:- Explain the formation of scum when hard water is treated with soap?
Ans:- Hard water contains salts of calcium and magnesium. Calcium and magnesium on reaction with soap (carboxylic acid) forms insoluble substance called scum.
Q.11:- What change will you observe if you test soap with litmus paper (red or blue)?
Ans:- Red litmus will turn blue because soap is alkaline.
Q.12:- What is hydrogenation? What is its industrial application?
Ans:- The addition of hydrogen to unsaturated hydrocarbon in the presence of catalyst is called hydrogenation.
Industrial application :- Vegetable oils have long unsaturated carbon chains. These on hydrogenation in the presence of nickel catalyst from saturated carbon chains which are animals fats or ghee. Thus ghee on industrial scale is made by hydrogenation of naturally available vegetable oils.
Q.13:- Which of the following hydrocarbons undergo addition reactions :-
C6H6, C3H8, C3H6, C2H2 and CH4.
Ans:- C3H6 and C2H2.
Q.14:- Give a test that can be used to differentiate chemically between butter and cooking oil.
Ans:- Cooking oil is unsaturated hydrocarbon whereas butter is saturated hydrocarbon. We know that brown color of bromine disappears when a drop of bromine is added to an unsaturated compound whereas there is no reaction between saturated hydrocarbons and bromine. Thus when a drop of bromine is added to cooking oil, its color disappears whereas when a drop of bromine is added to butter, it becomes brown.
Q.15:- Explain the mechanism of the cleaning action of a soaps.
Ans:- Soaps form micelles in water. The oily dirt from clothes get attached to the center of micelle. The micelles do not come close to each other and get separated due to ion-ion repulsion. The micelles containing oil dirt thus stay in solution as colloid and are easily rinsed away.
