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Science Answer the questions.[Che-5M]

MODEL PAPER - 9 [2026] · CBSE STD 10 (CBSE - English Medium). 2 questions.

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Answer the questions.[Che-5M]

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Question 15 Marks
Explain chlor-alkali process and write balanced chemical equations for the reactions that occur. Name the gases obtained at the anode and cathode respectively. Mention two uses each of the two gases obtained in the above process.
Answer
• Chlor-akali process - When electricity is passed through aqueous solution of sodium chloride (brine), it decomposes toform sodium hydroxide, chlorine and hydrogen.
• $2 NaCl(aq)-2 H_2 O(l) \rightarrow 2 NaOH+Cl_2+H_2$
• Anode - Chlorine gas $/ Cl _2$
• Cathode - Hydrogen gas: $H _2$
• $Cl_2$
1. Used in the preparation of bleaching powder.
2. To make drinking water free from germs or any other.
• $H_{2}$
1. Used in the manufacture of ammonia fertilisers.
2. Used in fuels and margarine.
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Question 25 Marks
In an industrial process used for the manufacture of sodium hydroxide, a gas $\mathbf{A}$ is formed as a by-product. The gas A reacts with lime water to give a compound $\mathbf{B}$ which is used as a bleaching agent in the chemical industry. Identify $\mathbf{A}$ and $\mathbf{B}$. Also give the chemical equations of the reactions involved.
Answer
In the manufacture of sodium hydroxide (Chlor-alkali process), hydrogen gas and chlorine gas are formed as by-products. The chemical equation for the reaction is as follows:-
$2 \mathrm{NaCl}(\mathrm{aq})+2 \mathrm{H}_{2} \mathrm{O}(\mathrm{l}) \rightarrow 2 \mathrm{NaOH}(\mathrm{aq})+\mathrm{Cl}_{2}(\mathrm{~g})+\mathrm{H}_{2}(\mathrm{~g})$
Gas 'A', which is formed as by-product and which also reacts with lime water (calcium hydroxide) to form calcium oxy-chloride isthus, chlorine. Gas A is not hydrogen. Calcium oxy-chloride is used as a bleaching agent in the chemical industry. The chemica lequation for the formation of calcium oxy-chloride is as follows:-
$\mathrm{Ca}(\mathrm{OH})_{2}(\mathrm{~s})+\mathrm{Cl}_{2}(\mathrm{~g}) \rightarrow \mathrm{CaOCl}_{2}(\mathrm{~s})+\mathrm{H}_{2} \mathrm{O}(\mathrm{l})$
Therefore, gas ' $\mathbf{A}$ ' is chlorine gas ( $C l_{2}$ ) and ' $\mathbf{B}$ ' is calcium oxy-chloride (bleaching powder).
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Answer the questions.[Che-5M] - Science STD 10 Questions - Vidyadip