Organic Chemistry Class-10 Goyal Brothers ICSE Solutions Ch-11

(i) C4H8


(i) C4H8





Draw position isomers of the following C5H8

Question 9. What are the general properties of homologous series?

Answer :Features include a general formula and neighbouring members differing by CH2, with similar chemical properties and with a gradation in physical properties. Homologous series are ‘families’ of organic compounds. They share common characteristics: They all contain the same functional group

Question 10.  Write the name and structural formula of the simplest organic acid.

Answer :

Simplest organic acid is Formic acid and the chemical formula is  .

Exercise 3 Page –203

Organic Chemistry Class-10 Goyal Brothers ICSE Solutions Ch-11

Question 1. How is methane gas prepared in the laboratory?

Answer : In the laboratory, methane is formed by heating sodium ethanoate with a mixture of sodium hydroxide and calcium oxide, called soda lime,  on heating in the presence of a catalyst, calcium oxide, the -COONa group from sodium ethanoate is replaced by the hydrogen atom from sodium hydroxide, forming methane and sodium hydroxide gets converted into sodium carbonate
Question 2. What do you understand by the term substitution reaction?

Answer : Substitution reaction, any of a class of chemical reactions in which an atom, ion, or group of atoms or ions in a molecule is replaced by another atom, ion, or group.
Question 3.  How does excess chlorine react with :

(i) methane

(ii) ethane?

Answer : excess chlorine react with :

(i) methane—When a mixture of methane and chlorine is exposed to ultraviolet light – typically sunlight – a substitution reaction occurs and the organic product is chloromethane. However, the reaction doesn’t stop there, and all the hydrogens in the methane can in turn be replaced by chlorine atoms

(ii) ethane–Ethane reacts with chlorine by free radical halogenation in the presence of sunlight when chlorine breaks down to form two chlorine radicals. The chlorine radical reacts with ethane to give ethane radical which reacts with other chlorine to generate to give halogenated product C2Cl6

Question 4. How is ethane gas prepared in the laboratory?

Answer : Ethane gas can be prepared in a laboratory by the cracking of hydrocarbons such as kerosene or candle wax. … The vapor of kerosene when passes over heated porcelain pieces undergoes cracking. The gas so formed is collected in gas jars by the downward displacement of water. This gas is mostly ethane (ethylene)
Question 5.  What do you understand by pyrolysis?

Answer : Pyrolysis is a thermochemical treatment, which can be applied to any organic (carbon-based) product. It can be done on pure products as well as mixtures. In this treatment, material is exposed to high temperature, and in the absence of oxygen goes through chemical and physical separation into different molecules
Question 6. How will you obtain ethane from ethyl iodide? Give chemical equation.

Answer :

Question 7. How do alkanes burn in:

(i) Excess air

(ii) Insufficient supply of air

Answer : alkanes burn in:

(i) Excess air—However, these alkanes burn very rapidly. The combination of alkanes with oxygen generating heat is known as combustion. More precisely, combustion is defined as “a chemical reaction with oxygen in which alkane is converted into carbon dioxide and water with the release of heat energy”

(ii) Insufficient supply of air–It occurs when there is not enough amount of oxygen for fuel to react completely. This leads to the formation of carbon or carbon monoxide. Carbon monoxide formed as a by product is a colourless poisonous gas.

Methane + (little) Oxygen → Carbon + Water

CH₄ + O₂ → C + 2H₂O

Question 8. Write names and structural formulae of isomers of fourth and fifth homologous members of alkanes.

Answer :

The fourth member of the alkane series is butane .

The fifth member of the alkane series is pentane

Question 9. How will you bring about the following conversions?
(i) Methane to methyl alcohol

(ii) Methane to methanoic acid

(iii) Ethane to acetaldehyde

Answer : the following conversions

(i) Methane to methyl alcohol–Methane, is first converted into methyl chloride by chlorination, in the presence of diffused sunlight. Methyl chloride on hydrolysis forms methyl alcohol.

(ii) Methane to methanoic acid–The progressive oxidation of methane by 2 electron losses to form methanol, formaldehyde and ultimately formic acid using simple vanadium compound with the use of H2O2.

Methane to methanoic acid

(iii) Ethane to acetaldehyde

The catalytic conversion of ethane to acetaldehyde has been achieved using nitrous oxide as the oxidant.  The resulting ethyl radical reacts with surface MoO to produce a surface ethoxide, which may either decompose to ethylene or react further with surface OH to form acetaldehyde or with water to form C2H5OH.

Ethane to acetaldehyde
Question 10.  Give two uses of

(i) Methane

(ii) Ethane

Answer : two uses of

(i)Methane— It is used primarily as fuel to make heat and light. It is also used to manufacture organic chemicals.

(ii)Ethane–The chief use of ethane is the production of ethene (ethylene) by steam cracking. … Ethane can be used as a refrigerant in cryogenic refrigeration systems. On a much smaller scale, in scientific research, liquid ethane is used to vitrify water-rich samples for electron microscopy

Exercise 4 Page –207

Organic Chemistry Class-10 Goyal Brothers ICSE Solutions Ch-11

Question 1. How will you prepare ethylene gas in the laboratory? Support your answer by chemical equations.

Answer :

Balanced Equation of ethylene:


How will you prepare ethylene gas in the laboratory

The gas is collected by downward displacement of water.

Question 2. How does ethylene react with (i) bromine (ii) alkaline potasium permanganate (iii) HCl gas?

Answer :

ethylene react with

(i) bromine — When bromine is passed through the inert solution of ethene, an addition reaction takes place with the formation of 1, 2, dibromoethane.

(ii) alkaline potasium permanganate— Ethene reacts with alkaline potassium permanganate solution to form glycol.

(iii) HCl gas—  Ethene reacts with HCl to form ethane glycol monochloride.

Question 3. State two uses of ethylene gas.

Answer : Uses of ethylene :

(i) It is used in the manufacture of polyethylene which is a valuable plastic.
(ii) It is used in the artificial ripening of fruits.

Question 4. Write the structural formula of isomers of the following: (i) Pentene (ii) Butene

Answer : isomers of the following:

(i) Pentene -It’s chemical formula is C5 H10. There are  three  isomers  of pentene: 1-pentene, with the double bond at carbon 1. cis-2-pentene, with the double bond at carbon 2, and the functional groups on the same side

(ii) Butene-The chemical formula for butene is: C4 H8, which means it’s made up of four carbon atoms and eight hydrogen atoms. The ‘-ene’ part of the name refers to an alkene, so we know that butene’s structure must include a carbon double bond

  • but-1-ene
  • but-2-ene)
  • 2-methylprop-1-ene

Question 5. Write the chemical equation for the preparation of ethylene gas by dehydrohalogenation with alcoholic potash.

Answer : preparation of ethylene gas by dehydrohalogenation with alcoholic potash.: Alcohols reacts with concentrated sulphuric acid which results in the formation of alkenes due to the elimination of a water molecule. As water molecule is removed in this reaction, it is called as acidic dehydration of alcohol and the dehydrating agent is concentrated sulphuric acid.

Question 6. Why does ethene give addition reactions?

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