Seawater contains many salts dissolved in it. Common salt is separated from these salts. Deposits of solid salt are also found in several parts of the world. These large crystals are often brown due to impurities. This is called rock salt and is mined like coal. The common salt is an important raw material for chemicals of daily use. (a) Write balanced chemical equations to show the products formed during electrolysis of brine. [1] (b) List two uses of any one product obtained during electrolysis of brine. [1] (c) (i) A mild non-corrosive basic salt 'A', used for faster cooking, is strongly heated to produce a compound 'B', that is used for removing permanent hardness of water. Identify A and B and also write the equation for the reaction that occurs when A is heated. [2] OR (c) (ii) Define water of crystallisation. Give two examples of salts that have water of crystallisation. [2]
Seawater contains many salts dissolved in it. Common salt is separated from these salts. Deposits of solid salt are also found in several parts of the world. These large crystals are often brown due to impurities. This is called rock salt and is mined like coal. The common salt is an important raw material for chemicals of daily use. (a) Write balanced chemical equations to show the products formed during electrolysis of brine. [1] (b) List two uses of any one product obtained during electrolysis of brine. [1] (c) (i) A mild non-corrosive basic salt 'A', used for faster cooking, is strongly heated to produce a compound 'B', that is used for removing permanent hardness of water. Identify A and B and also write the equation for the reaction that occurs when A is heated. [2] OR (c) (ii) Define water of crystallisation. Give two examples of salts that have water of crystallisation. [2]
(a) 2NaCl + 2H2O 2NaOH + Cl2 + H2 (at cathode) 2H+ + 2e- H2 (at anode) (b) Two uses of sodium hydroxide are: (i) manufacture of soap (ii) manufacture of paper (c) (i) A is sodium carbonate (Na2CO3) and B is sodium oxide (Na2O). 2Na2CO3 2Na2O + 2CO2 (c) (ii) Water of crystallisation is the fixed number of water molecules present in the crystals of a salt. Two examples are: (i) blue vitriol - CuSO4.5H2O (ii) washing soda - Na2CO3.10H2O
Marking Scheme
- 14 marks
Hint
The electrolysis of brine produces sodium hydroxide, chlorine gas, and hydrogen gas.
Quick Oral Answer
The electrolysis of brine produces sodium hydroxide, chlorine gas, and hydrogen gas. Sodium hydroxide is used in various industrial processes, such as the manufacture of soap and paper.
Analysis & Explanation
The electrolysis of brine produces sodium hydroxide, chlorine gas, and hydrogen gas. Sodium hydroxide is used in various industrial processes, such as the manufacture of soap and paper. Sodium carbonate is heated to produce sodium oxide, which is used to remove permanent hardness of water. Water of crystallisation is the fixed number of water molecules present in the crystals of a salt.
Common Mistakes
- 1confusing electrolysis with other industrial processes
Interesting Facts
the electrolysis of brine is used in various industrial processes, such as the production of chlorine gas and sodium hydroxide
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Frequently Asked Questions
How many marks does this question carry in CBSE Class 10 Science 2025?
This question carries 4 marks in the CBSE Class 10 Science 2025 examination.
Which chapter does this question come from in Science?
This question is from the chapter "Acids, Bases and Salts" in the CBSE Class 10 Science syllabus.
What topic does this question cover in Science?
This question covers the topic "Chemical Properties of Acids and Bases" from CBSE Class 10 Science.
What type of question is this in the CBSE Class 10 Science 2025 paper?
This is a Essay question from Section E in the CBSE Class 10 Science 2025 paper.