NCERT Solutions for Class 10 Science Chapter-4 “Carbon And Its Compounds”
Answer The Following Question.
1. What would be the electron dot structure of carbon dioxide
which has the formula of CO2?
Answer:
2. What would be the electron dot structure of a molecule of
sulphur which is made up of eight atoms of sulphur?
Answer:
3. How many structural isomers can you draw for pentane?
Answer:
The isomers are as follows:
4. What are two properties of carbon which lead to the huge
number of carbon compounds we see around us?
Answer:
The two properties are :
(a) catenation- the ability to form bonds with other atoms of
carbon.
(b) Tetravalency of carbon.
5. What will be the formula and electron dot structure for
cyclopentane?
Answer:
The formula of cyclopentane is C5H10. The electron dot structure cyclopentane is:
6. Draw the structure for the following compounds :
(i) Ethanoic acid
(ii) Bromopentane
(iii) Butane
(iv) Hexanal
Answer:
Structure of compounds are given as under:
(i) Ethanoic acid
(ii) Bromopentane
(iii) Butanone
(iv) Hexanal
7. How would you name the following compounds?
Answer:
(i) Bromomethane
(ii) Methanal (Formaldehyde)
(iii) Hexyne
8. Would you be able to check if water is hard by using a detergent?
Answer:
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?
Answer:
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
Answer:
(b) 7 covalent bonds
11. Butanone is a four carbon compound with the functional group
(a) carboxylic acid
(b) aldehyde
(c) ketone
(d) alcohol
Answer:
(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.
Answer:
(b) the fuel is not burning completely.
13. Explain the nature of the covalent bond using the bond
formation in CH3Cl.
Answer:
A 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
Answer:
(a) Ethanoic acid
(b) H2S
(c) Propanone
(d) F2
15. What is a homologous series? Explain with an example.
Answer:
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?
Answer:
On the basis of physical properties :
Melting and boiling points of ethanol is 156 K and 351 K but the melting and
boiling points 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?
Answer:
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?
Answer:
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.
Answer:
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)?
Answer:
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?
Answer:
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
Answer:
C3H6 and C2H2 will
undergo addition reactions.
23. Give a test that can be used to differentiate chemically
between butter and cooking oil?
Answer:
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.
Answer:
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.
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