NCERT Solutions for Class 10 Science chapter-4 Carbon And Its Compounds
1. What would be the
electron dot structure of carbon dioxide which has the formula of CO2?
Solution :
2. What would be the
electron dot structure of a molecule of sulphur which is made up of eight atoms
of sulphur?
Solution :
3. How many structural
isomers can you draw for pentane?
Solution : The isomers are as under:
4. What are two
properties of carbon which lead to the huge number of carbon compounds we see
around us?
Solution : The two properties are :
(a) catenation- the
ability to form bonds with other atoms of carbon.
(b) Tetravalancy of
carbon.
5. What will be the
formula and electron dot structure for cyclopentane?
Solution : Formula of cyclopentane is C5H10.
The electron dot structure cyclcopente is:
6. Draw the structure
for the following compounds :
(i) Ethanoic acid
(ii) Bromopentane
(iii) Butane
(iv) Hexanal
Solution : Structure of compounds are given as
under :
(i) Ethanoic acid
(ii) Bromopentane
(iii) Butanone
(iv) Hexanal
7. How would you name
the following compounds?
Solution :
(i) Bromomethane
(ii) Methanal
(Formaldehyde)
(iii) Hexyne
8. Would you be able
to check if water is hard by using a detergent?
Solution : No, we would be able to check if water
is hard by using a detergent.
9. People use a
variety of methods to wash clothes. Usually after adding the soap, they beat
the clothes on stone, or beat it with a paddle, scrub with a brush or the
mixture is agitated in a washing machine. Why is agitation necessary to get
clean clothes?
Solution : Agitation is necessary to obtain
complete mecells formation and the emulsion of oil in water so that the whole
of dirt is removed on rinsing with water.
10. Ethane, with the
molecular formula C6 has
(a) 6 covalent bonds
(b) 7 covalent bonds
(c) 8 covalent bonds
(d) 9 covalent bonds
Solution : (b) 7 covalent bonds
11. Butanone is a four
carbon compound with the functional group
(a) carboxylic acid
(b) aldehyde
(c) ketone
(d) alcohol
Solution : (c) Ketone
12. While cooking, if
the bottom of the vessels is getting blackened on the outside, it means that
(a) the fuel is not
cooked completely.
(b) the fuel is not
burning completely.
(c) the fuel is wet.
(d) the is burning
completely.
Solution : (b) the fuel is not burning completely.
13. Explain the nature
of the covalent bond using the bond formation in CH3Cl.
Solution : Covalent bond is formed by sharing of
electrons between two atoms. It is non-ionic in nature.
14. Draw the electron
dot structure for
(a) Ethanoic acid
(b) H2S
(c) Propanone
(d) F2
Solution :
(a) Ethanoic acid
(b) H2S
(c) Propanone
(d) F2
15. What is a
homologous series? Explain with an example.
Solution : Series of compounds in which the same
functional group substitutes for hydrogen in a carbon chain is called
homologues series. The difference between the formulae of any two successive
members is –CH2 and difference between the molecular formula is
14 u.
16. How can ethanol
and Ethanoic acid be differentiated on the basis of their physical and chemical
properties?
Solution :
On the basis of
physical properties :
Melting and boiling points of ethanol is 156 K and 351 K but melting and
boiling point of Ethanoic acid is 290K and 391K respectively.
On the chemical
properties :
Ethanoic acid reacts with sodium hydrogen carbonate liberating carbon dioxide
while ethanol does not.
17. Why does micelle
formation take place when soap is added to water? Will a micelle be formed in
other solvents such as ethanol also?
Solution : Soap is sodium or potassium salt of long
chain fatty acid. Two ends of soap molecules have different properties. The
ionic end is hydrophilic. It dissolve in water while the hydrogen chain is
hydrophobic, it dissolve in hydrocarbon. The hydrocarbon chains are oriented
towards the oil droplet while the ionic ends are oriented towards water.
Micelles formation will not take place in ethanol.
18. Why are carbon and
its compounds used as fuels for most applications?
Solution : Carbon on combustion gives carbon
dioxide and water. This reaction is accompanied by evolution of heat and light.
The same is true for compounds of carbon. That is why carbon and its compounds
are used as fuel for most applications.
19. Explain the
formation of scum when hard water is treated with soap.
Solution : Hard water contains hydrogen carbonates,
chlorides and sulphates of calcium and magnesium which reacts with soap to form
scum. For example, calcium chloride reacts with soap to form scum.
Sodium stearate + Calcium chloride à sodium chloride + Calcium stearate(scum)
20. What change will
you observe if you test soap with litmus paper (red and blue)?
Solution : Soap is sodium or potassium salt of
fatty acid. It is obtained by treating of oil with caustic soda. Sodium
stearate is thus a salt of weak acid and strong base. Its water solution will
be slightly alkaline and will turn red litmus red.
21. What is
hydrogenation? What is its industrial application?
Solution : Unsaturated hydrocarbons add hydrogen in
presence of catalysts such as palladium or nickel to give saturated
hydrocarbons. This process is called hydrogenation.
It is commercially used for converting vegetable oils to ‘vanaspati’ ghee in
presence of nickel as catalyst.
22. Which of the
following hydrocarbons undergo addition reactions?
C6, C3H8,
C3H6, C2 and CH4
Solution : C3H6 and C2H2 will
undergo addition reactions.
23. Give a test that
can be used to differentiate chemically between butter and cooking oil?
Solution : Butter and cooking oil can be
differentiated with the help of bromine water test. Cooking oil will decolorize
the red colour of bromine water on shaking while butter will not.
24. Explain in
mechanism of the cleaning action of soap.
Solution : Soap are sodium or potassium salt of
fatty acids. Two ends of molecules of soap behave differently. This ionic end
is hydrophilic and it is oriented towards water. The other hydrocarbon end is
hydrophobic and it is oriented towards dirt which is oily in nature. A micelle
formation around the oily dirt takes place. When flushed with excess of water,
the micelle containing the dirt is removed, thus cleaning the clothes, etc.
Either way the teacher or student will get the solution to the problem within 24 hours.