Carbon And It's Compounds
Class: 10 | Chapter: 4
Extra Questions & Answer
1. Why are unsaturated hydrocarbons more reactive than saturated hydrocarbons?Ans. Unsaturated hydrocarbons are more reactive than saturated hydrocarbons becouse they have the presence of week pi bonds which easily break down and thus reaction takes place.
2. How many covalent bonds are there in a molecule of cyclohexane?
Ans. 18 Covalent Bonds ( 6 C-C, 12 C-H)
3. Give the general formula of paraffins, olefins and alkynes.
Ans. Alkanes are also called paraffins and have general formula : CnH2n+2 Olefins are also called alkenes and have general formula : CnH2n Alkynes have general formula : CnH2n-2
4. Why are carbon and it's compounds used as fuel for most applications?
Ans. Carbon And it's compounds have high calorific value. When we burn them, they give high energy, light with no smoke. That's why they are used as fuel.
5. Why are carbon compounds not able to conduct electricity through them?
Ans. Carbon has 4 electrons in valence shell and it forms it's compounds by covalent bonding by sharing all the 4 electrons. It is not having any free electron to move in the structure . Therefore, carbon compounds are not able to conduct electricity.
6. Would you able to check if water is hard using a detergent?
Ans. No, becouse detergents can work in hard water also.
7. Explain the formation of scum when hard water is treated with soap?
Ans. Hard water has calcium and magnesium ions in it. When these ions react with soap , they form insoluble calcium and magnesium fatty acid salts which appear white curdy precipitate. This is called scum.
8. Give a test that can be used to differentiate chemically between butter and cooking oil.
Ans. Chemically butter is saturated and cooking oil is unsaturated in nature. So, we can confirm it by alkaline KMnO4 or Bromine water test. Alkaline KMnO4 loses its pink colour in presence of cooking oil whereas in case of butter it remains. In the same way ,brown colour of bromine water also goes away in cooking oil.
9. An organic compound 'A' is a consituent of antifreeze. The compound on heating with oxygen forms another compound B which has a molecular formula C2H4O2. Identify the compound 'A' and 'B'.write the chemical equation of the reaction that takes place to form the compound 'B'.
Ans. Compound 'A' is ethanol. It oxidises to give ethanoic acid in presence of alkaline KMnO₄.
CH3CH2OH + 2[O] ---------------------> CH3COOH + H2O
10. The molecules of alkene family are represented by a general formula CnH2n.
I. What do n and 2n signify?
II. What is the name of alkene when n=3?
Ans. (I) Here n tells the no. of carbon atoms and 2n represents the no. of hydrogen atoms in alkenes.
(II) It is propene ( C3H6).
11. Name the unique ability of carbon to form bonds with other atoms of carbon.
Ans. Catenation.
12. Mention the two characteristic features seen in carbon.
Ans. 1. Catenation
2. Tetravalency
13. Name the first organic compound synthesised by Wohler.
Ans. Urea
14. Write the general molecular formula of alkane series.
Ans. CnH2n+2
15. Write the IUPAC name of the following compound:
CH3CH2CH2CH2—C ≡ C—H
Ans. 1- Hexyne.
16. Write the name and formula of the 2nd member of homologous series having general formula CnH2n.
Ans. This is the general formula of Alkenes and it's second member is propene (C3H6).
17. Write the molecular formula of an alkyne containing 10 atoms of hydrogen.
Ans. C6H10.
18. Why is ethanoic acid known as glacial acetic acid?
Ans. Ethanoic acid forms ice like structure below room temperature i. e. 16.7°C.Therefore it is called glacial acetic acid.
19. Which property of ethanol makes it suitable for preparing medicines such as tincture iodine, cough syrup and other tonics?
Ans. Ethanol has anti - septic properties and moreover it can dissolve the lipids presents on cell membranes of pathogens and thus can kill them . Therefore it is suitable for preparing medicines such as tincture of iodine, cough syrup and other tonics.
20. Name the alcohol which is an active ingredient of all alcoholic drinks.
Ans. Ethanol.
21. Which two of the following compounds could belong to the same homologous series?
C2H6O2, C2H6O, C3H28, CH4O.
Ans. C2H6O and CH4O belong to same homologous series, alcohol.
22. Among CH4, C2H6 and C4H10 which is expected to show isomerism?
Ans. C4H10, butane.
23. Name the oxidising agent which can oxidise ethanol to ethanoic acid.
Ans. Alkaline KMnO₄ and Acidified K₂Cr₂O₇.
24. Write the formula and name of next homologue of CH3COCH3.
Ans. CH3CH2COCH3, Butanone.
25. Why do alkanes burn with a blue flame?
Ans. Alkanes burn / oxidise completely in air and have low percentage of carbon.
26. How do the melting and boiling points of the hydrocarbons change with increase in molar mass?
Ans. With increase in molar mass of hydrocarbons, van der waals intractions increase and hence more temperatures are needed to melt or boil the hydrocarbons.
27. Which of the following hydrocarbons can undergo addition reactions:
C2H6, C4H10, C3H6, C3H4, CH4, C2H2, C4H8
Ans. Unsaturated compounds undergo addition reactions. Therefore, C3H6, C3H4, C2H2 and C4H8 show this type of reaction.
28. Give the general formula of alkanes. Write the name, structural formula and physical state of the compound containing:
(i) 3-carbon atoms
(ii) 8-carbon atoms.
Ans. General formula of alkanes : CnH2n+2
(i) C3H8, Propane , gaseous state.
(ii) C8H18, Octane, liquid.
29. List the common physical properties of carbon compounds.
Ans. 1. Low melting and boiling point.
2. Poor conductors of electricity.
3. Week forces of interaction.
30. Draw the structures of diamond and graphite.
Ans. Structure of diamond : diamond has gaint 3D structure in which each carbon atom is bonded to four other carbon atoms tetrahedrally.
Ans. Uses of methyl alcohol : 1. It is used as a solvent in making inks, resins.
2. It is used in manufacturing of plastics, polyesters and other chemicals.
Uses of ethyl alcohol : 1. It is used as a beverage.
2. It is used as an antifreeze for automobile radiators.
32. List two main points of difference between organic and inorganic compound.
Ans. Organic compounds : 1. Organic compounds generally contain carbon atom and they form covalent bonds.
2. Organic compounds exist in all physical states.
Inorganic compounds : 1. Inorganic compounds don't contain carbon and they are formed by ionic bonding.
2. Inorganic compounds exist mainly in solid state.
33. What are substitution reactions? Justify your answer with a suitable example.
Ans. Substitution reactions : when in a reaction, hydrogen atoms are replaced by some other atoms or groups, these reactions are known as substitution reactions. For example:
CH4 + Cl2 ---------------------> CH3Cl + HCl
34. Give any four uses of ethanoic acid.
Ans. Uses of ethanoic acid : 1. In making paints, medicines.
2. As a solvent.
3. In the manufacture of perfumes and dyes.
4. For making vinegar.
35. List four differences between soaps and detergents.
Ans. Soaps : 1. These are sodium or potassium sakrs of fatty acids.
2. These are biodegradable.
3. These are not efficient in hard water.
4. These are mild cleansers.
Detergents :1. These are sodium salts of alkylbenzene sulphonic acid or alkylhydrogensulphates.
2. These are non - biodegradable.
3. These are efficient in hard water also.
4. These are strong cleansers.
36. The molecular formula of an organic compound X is C2H4O2 which has vinegar like smell.
(i)Write its chemical formula and name.
(ii) What happens when sodium bicarbonate is added into it?
Ans. (i) The compounds is CH3COOH, ethanoic acid. (ii) CH3COOH + NaHCO3 -------------> CH3COONa + H2O + CO2. When Ethanoic acid reacts with sodium bicarbonate, a rapid evolution of CO2 occurs.
37. Write the molecular formula of first two members of homologous series having functional group-Cl.
Ans. CH3Cl, CH3CH2Cl.
38. Which functional groups always occur at the terminal position of a carbon chain?
Ans. -CHO ( Aldehyde) and -COOH ( Carboxylic acids) .
39. Name the functional group which always occurs in the middle of a carbon chain.
Ans. Ketone
40. In an organic compound, which parts largely determine its physical and chemical properties?
Ans. Alkyl chain determines physical properties and functiinal groups determines chemical properties of organic compounds.
41. Which of the following are alkenes ?
CH4, C2H6, C2H4, C3H6and C3H8.
Ans. Alkenes have general formula CnH2n . So, acc. to that C2H4, C3H3 are alkenes.
42. What happens when methane is burnt in air?
Ans. When methane is burnt in air, we get carbon dioxide gas and water as product.
CH4 + O2 ---------------> CO2 + H2O
43. What is the next holologue of C3H7OH called ?
Ans. Butanol, C4H9OH.
44. How many valence electrons are there in carbon atom?
Ans. Four electrons.
45. Write the name and formula of 2nd member of homologous series having general formula Cn H2n+2.
Ans. This is the general formula for alkanes. It's second member is ethane (C2H6).
46. Define allotropy.
Ans. Allotropy : when element exist in different physical forms, containing sane chemical properties but different physical properties, the different physical forms are called allotropes of that element and this phenomenon is called allotropy.
47. Carbon, Group (14) element in the Periodic Table, is known to form compounds with many elements.
Write an example of a compound formed with:
(a) Chlorine (Group 17 of Periodic Table)
(b) Oxygen (Group 16 of Periodic Table).
Ans. (a) CCl4, carbon tetrachloride
(b) CO2, Carbon dioxide
48. How is ethanol obtained for commercial use ?
Ans. Ethanol is obtained on commercial scale by fermentation of sugar.
C12H22O11 + H2O -----------------> C6H12O6 + C6H12O6
(sucrose) invertase ( glucose) (fructose)
C6H12O6 -------------------> 2C2H5OH + 2 CO2
(glucose / fructose) (ethanol)
49. Name the gas evolved when ethanoic acid reacts with sodium carbonate. How would you identify this gas?
Ans. Carbon dioxide gas.
Identification Test : When this gas passed through lime water, it gives milky appreance.
50. What is meant by denatured alcohol ? What is the need to denature alcohol ?
Ans. Denatured alcohol : When ethyl alcohol is mixed with poisonous substances like methanol, copper sulphate, pyridine etc., it is called denatured alcohol.
To prevent ethyl alcoho's misuse for drinking purposes , industries make it denatured.