CBSE Class 10 Science HOTs Carbon And its Compounds Set 08

Question. State the observation : Bromine vapours are passed into a soln. of ethyne in carbon tetrachloride.
Answer: Ethyne decolourizes the reddish brown colour of bromine solution.

Question. From – Ethyne, ethanol, acetic acid, ethene, methane. Choose the one which relates to : An unsaturated hydrocarbon used for welding purposes.
Answer: Ethyne

Question. From – Ethyne, ethanol, acetic acid, ethene, methane. Choose the one which relates to : An organic compound whose functional group is carboxyl.
Answer: Acetic acid

Question. From – Ethyne, ethanol, acetic acid, ethene, methane. Choose the one which relates to : A hydrocarbon which on catalytic hydrogenation gives a saturated hydrocarbon.
Answer: Ethene

Question. From – Ethyne, ethanol, acetic acid, ethene, methane. Choose the one which relates to : An organic compound used as a thermometric liquid.
Answer: Ethanol

Question. Why is pure acetic acid known as glacial acetic acid?
Answer: Pure acetic acid freezes below 20°C to form a transparent solid which looks like ice and hence, it is called glacial acetic acid.

Question. Give a chemical equation for the reaction between ethyl alcohol and acetic acid.
Answer: \( \text{C}_2\text{H}_5\text{OH} + \text{CH}_3\text{COOH} \xrightarrow{\text{conc. H}_2\text{SO}_4} \text{CH}_3\text{COOC}_2\text{H}_5 + \text{H}_2\text{O} \)

Question. Rewrite the correct statement with the missing word/s. Ethyl alcohol is dehydrated by sulphuric acid at a temperature of about 170°C.
Answer: Ethyl alcohol is dehydrated by concentrated sulphuric acid at a temperature of about 170°C.

Question. Give the structural formula for : Methanoic acid
Answer:

  O
  ||
H-C-OH

Question. Give the structural formula for : Ethanal
Answer:

  H O
  | ||
H-C-C-H
  |
  H

Question. Give the structural formula for : Ethyne
Answer:

H-C≡C-H

Question. Give the structural formula for : Acetone
Answer:

  H O H
  | || |
H-C-C-C-H
  |   |
  H   H

Question. Give the structural formula for : 2-methyl propane
Answer:

  H   H   H
  |   |   |
H-C - C - C-H
  |   |   |
  H   |   H
    H-C-H
      |
      H

Question. Identify the gas evolved when : sodium propionate is heated with soda lime.
Answer: Ethane gas

Question. Give suitable chemical term for : A reaction in which hydrogen of an alkane is replaced by a halogen.
Answer: Substitution reaction

Question. Give a chemical test to distinguish between : Ethene gas and ethane gas.
Answer: To the given gas add few drops of bromine solution in carbon tetrachloride. In case of ethene gas, the reddish colour of bromine discharges. However, in case of ethane gas the reddish colour of bromine does not discharge.

Question. Identify the statement that is incorrect about alkanes :
(a) They are hydrocarbons.
(b) There is single covalent bond between carbon and hydrogen
(c) They can undergo both substitution as well as addition reactions
(d) On complete combustion they produce carbon dioxide and water.
Answer: (c) They can undergo both substitution as well as addition reactions

Question. Give balanced chemical equation for the laboratory preparation of : A saturated hydrocarbon from iodomethane.
Answer: \( \text{CH}_3\text{I} + 2\text{H (from Zn/Cu couple)} \rightarrow \text{CH}_4 + \text{HI} \)

Question. Give balanced chemical equation for the laboratory preparation of : An unsaturated hydrocarbon from an alcohol.
Answer: \( \text{C}_2\text{H}_5\text{OH} + \text{H}_2\text{SO}_4\text{ (conc)} \xrightarrow{160^\circ\text{C}} \text{C}_2\text{H}_4 + \text{H}_2\text{SO}_4 \cdot \text{H}_2\text{O} \)

Question. Give balanced chemical equation for the laboratory preparation of : An unsaturated hydrocarbon from calcium carbide.
Answer: \( \text{CaC}_2 + 2\text{H}_2\text{O} \rightarrow \text{Ca(OH)}_2 + \text{C}_2\text{H}_2 \)

Question. Give balanced chemical equation for the laboratory preparation of : An alcohol from ethyl bromide.
Answer: \( \text{C}_2\text{H}_5\text{Br} + \text{KOH(aq)} \rightarrow \text{C}_2\text{H}_5\text{OH} + \text{KBr} \)

Question. Give the structural formula for : An isomer of n-butane.
Answer: [Iso-butane]

  H   H   H
  |   |   |
H-C - C - C-H
  |   |   |
  H   |   H
    H-C-H
      |
      H

Question. Give the structural formula for : 2-propanol.
Answer:

  H   H   H
  |   |   |
H-C - C - C-H
  |   |   |
  H  OH   H

Question. Give the structural formula for : Diethyl ether.
Answer:

  H   H   O   H   H
  |   |  ||   |   |
H-C - C - C - C - C-H
  |   |       |   |
  H   H       H   H

Question. Give reason: Methane does not undergo addition reactions, but ethene does.
Answer: All the four covalent bonds between the carbon and hydrogen are fully shared. Thus the hydrogen atom can only be substituted by more reactive atoms or group of atoms. There is no scope of addition of reactive atoms in its molecule.
However, in case of ethene there is a double bond between the two carbon atoms. These bonds are under strain and hence can be easily broken by more reactive atoms to form addition compounds which are saturated in nature.

Question. Give reason: Ethyne is more reactive than ethane.
Answer: Ethyne has a triple covalent bond \( (-\text{C} \equiv \text{C}-) \) between two carbon atoms, whereas ethene has a double covalent bond \( (-\text{C} = \text{C}-) \) between the two carbon atoms. So, the strain in the bounding of ethyne is far more than ethene. This accounts of the reactivity of ethyne as its bonds break more easily than that of ethene.

Question. Give reason: Hydrocarbons are excellent fuels.
Answer: All the constituents of hydrocarbon (carbon and hydrogen) are highly combustible and do not have any uncombustible content. So, hydrocarbons are excellent fuels.

Question. The I.U.P.C. name of acetylene is:
(a) propane
(b) propyne
(c) ethene
(d) ethyne
Answer: (d) ethyne

Question. Ethanol reacts with sodium to give......... (sodium ethanoate, sodium ethoxide, sodium propanoate)
Answer: sodium ethoxide

Question. Give one word or phrase for – hydrocarbons containing a \( \text{C}=\text{O} \) functional group.
Answer: Alkanone or Ketonic functional group

Question. Write balanced equation for preparation of : ethane from sodium propionate.
Answer: \( \text{CH}_3\text{-CH}_2\text{-COONa} + \text{NaOH} \xrightarrow[\Delta]{\text{CaO}} \text{C}_2\text{H}_6 + \text{Na}_2\text{CO}_3 \)

Question. Write balanced equation for preparation of : ethanol from monochloroethane and aq. sodium hydroxide.
Answer: \( \text{C}_2\text{H}_5\text{Cl} + \text{NaOH(aq)} \xrightarrow{\text{boil}} \text{C}_2\text{H}_5\text{OH} + \text{NaCl} \)

Question. Distinguish between : Ethane and ethene (using alkaline potassium permanganate solution)
Answer: Ethene decolourises the colour of alkaline \( \text{KMnO}_4 \) but ethane does not.

Question. State the conditions required for : Catalytic hydrogenation of ethyne.
Answer: One volume of ethyne gas is mixed with two volumes of hydrogen gas and passed over heated nickel at 300°C, when an addition reaction takes place with the formation of ethane gas.
\( \text{CH} \equiv \text{CH} + \text{H}_2 \xrightarrow[\text{300}^\circ\text{C}]{\text{Ni}} \text{CH}_2 = \text{CH}_2 \xrightarrow[\text{300}^\circ\text{C}]{\text{Ni}} \text{CH}_3 - \text{CH}_3 \)

Question. State the conditions required for : Preparation of ethyne from ethylene dibromide.
Answer: Zinc dust is added to a mixture of 95% ethyl alcohol and 5% of ethylene dibromide. The mixture is gently warmed when ethyne gas is liberated.
\( \text{CH(Br)}=\text{CH(Br)} + \text{Zn} \xrightarrow[\text{warm}]{\text{95\% alcohol}} \text{CH}\equiv\text{CH} + \text{ZnBr}_2 \)

Question. Write structural formula of : Ethanol
Answer:

  H   H
  |   |
H-C - C - OH
  |   |
  H   H

Question. Write structural formula of : 1-propanal
Answer:

  H   H   O
  |   |  ||
H-C - C - C - H
  |   |
  H   H

Question. Write structural formula of : ethanoic acid
Answer:

  H   O
  |  ||
H-C - C - OH
  |
  H

Question. Write structural formula of : 1, 2, dichloroethane
Answer:

  H   H
  |   |
H-C - C - H
  |   |
 Cl  Cl

Question. Match A and B with (i) and (ii) :
A: alkynes (1) \( \text{C}_n\text{H}_{2n+2} \)
B: alkane (2) \( \text{C}_n\text{H}_{2n-2} \)
Answer: A: alkynes (2) \( \text{C}_n\text{H}_{2n-2} \)
B: alkane (1) \( \text{C}_n\text{H}_{2n+2} \)

Question. Select from the list — Ammonia, ethane, hydrogen chloride, hydrogen sulphide, ethyne : The gas is used for welding purposes.
Answer: Ethyne

Question. Select from the list — Ammonia, ethane, hydrogen chloride, hydrogen sulphide, ethyne : This gas is also a saturated hydrocarbon.
Answer: Ethane

Question. State which of the following statements does not describe the property of alkenes :
(a) They are unsaturated hydrocarbons
(b) They decolourise bromine water
(c) They can undergo addition as well as substitution reactions
(d) They undergo combustion with oxygen forming carbon dioxide and water.
Answer: (c) They can undergo addition as well as substitution reactions. Alkenes do not undergo substitution reaction.

Question. State one appropriate observation when : The gaseous product obtained by dehydration of ethyl alcohol is passed through bromine water.
Answer: The reddish brown colour of bromine solution gets decolourised.

Question. Give balanced chemical equation for the conversion : Ethanoic acid to ethyl ethanoate.
Answer: \( \text{CH}_3\text{COOH} + \text{C}_2\text{H}_5\text{OH} \xrightarrow[\text{Warm}]{\text{Conc. H}_2\text{SO}_4} \text{CH}_3\text{COOC}_2\text{H}_5\text{ (Ethyl ethanoate)} + \text{H}_2\text{O} \)

Question. Give balanced chemical equation for the conversion : Calcium carbide to ethyne.
Answer: \( \text{CaC}_2 + 2\text{H}_2\text{O} \rightarrow \text{Ca(OH)}_2 + \text{CH} \equiv \text{CH} \)

Question. Give balanced chemical equation for the conversion : Sodium ethanoate to methane.
Answer: \( \text{CH}_3\text{COONa} + \text{NaOH} \xrightarrow[\text{300}^\circ\text{C}]{\text{CaO}} \text{Na}_2\text{CO}_3 + \text{CH}_4 \)

Question. Using structural formula identify the functional group of : Dimethyl ether.
Answer: The functional group is the ether group (-O-).

  H   H
  |   |
H-C-O-C-H
  |   |
  H   H

Question. Using structural formula identify the functional group of : Propanone.
Answer: The functional group is the ketonic group (>C=O).

   O
   ||
H3C-C-CH3

Question. Name the following : Process by which ethane is obtained from ethene.
Answer: Hydrogenation (addition)

Question. Name the following : A hydrocarbon which contributes towards the greenhouse effect.
Answer: Methane

Question. Name the following : Distinctive reaction that takes place when ethanol is treated with acetic acid.
Answer: Esterification

Question. Name the following : The property of element by virtue of which atoms of the element can link to each other in the form of a long chain or ring structure.
Answer: Catenation

Question. Name the following : Reaction when an alkyl halide is treated with alcoholic potassium hydroxide.
Answer: Dehydrohalogenation

Question. Conversion of ethene to ethane is an example of............ (hydration / hydrogenation).
Answer: hydrogenation

Question. Write balanced chemical equation for : Preparation of ethanol from ethyl chloride.
Answer: \( \text{C}_2\text{H}_5\text{Cl} + \text{NaOH(aq)} \rightarrow \text{C}_2\text{H}_5\text{OH} + \text{NaCl} \)

Question. Identify the term/substance : The catalyst used in the conversion of ethyne to ethane.
Answer: Nickel or platinum or palladium.

Question. Identify the term/substance : The type of reactions alkenes undergo.
Answer: Addition reactions.

Question. Write the IUPAC name of :

  H   H   H
  |   |   |
H-C = C - C - H
          |
          H

Answer: Propene

Question. Write the IUPAC name of :

  H       H
  |       |
H-C - C ≡ C - C - H
  |       |
  H       H

Answer: 2-butyne

Question. Write the IUPAC name of :

  H   H
  |   |
H-C - C = O
  |
  H

Answer: ethanal

Question. Write a balanced chemical equation for : Burning of ethane in plentiful supply of air.
Answer: \( 2\text{C}_2\text{H}_6 + 7\text{O}_2 \rightarrow 4\text{CO}_2 + 6\text{H}_2\text{O} \)

Question. Write a balanced chemical equation for : Action of water on calcium carbide.
Answer: \( \text{CaC}_2 + 2\text{H}_2\text{O} \rightarrow \text{Ca(OH)}_2 + \text{C}_2\text{H}_2 \)

Question. Write a balanced chemical equation for : Heating of Ethanol at 170°C in the presence of conc. sulphuric acid.
Answer: \( \text{C}_2\text{H}_5\text{OH} \xrightarrow[\text{170}^\circ\text{C}]{\text{conc. H}_2\text{SO}_4} \text{C}_2\text{H}_4 + \text{H}_2\text{O} \)