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Answer the following. (Science 2023 31/4/1 Q27)

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ScienceCBSE Class 10 · Board exam 2023, set 31/4/1 · 3 marks · Short answer

CBSE Class 10 Science 2023: question 27

Set in the CBSE Class 10 board exam of 2023, paper 31/4/1, section C, question 27, for 3 marks. Try it first; the hints and our step-by-step solution are below.

Q27 · 3 marks · Short answerChemical Reactions and Equations

Answer the following.

  1. (i)

    While electrolysing water before passing the current some drops of an acid are added. Why ? Name the gases liberated at cathode and anode. Write the relationship between the volume of gas collected at anode and the volume of gas collected at cathode.

    2 marks
  2. (ii)

    What is observed when silver chloride is exposed to sunlight ? Give the type of reaction involved.

    1 mark

Source: official question paper from cbse.gov.in (PDF). See it in the full 2023 board paper, set 31/4/1.

Hints

Open one hint at a time and try again before the next.

Hint 1

Does pure water conduct electricity well? What do the acid drops supply?

Hint 2

Positive ions move to the negative electrode. Look at the formula to find the gas ratio.

Hint 3

Silver chloride breaks down in light. What colour is finely divided silver?

Step-by-step solution

Each step shows the marks it earns, as an examiner would award them. Checked by an independent re-solve from the question paper.

  1. (i) A few drops of acid are added to increase the electrical conductivity of water. Pure water is a poor conductor because it has very few ions.

    ½ mark

  2. Gas at cathode: **hydrogen (). Gas at anode: oxygen ()**.

    1 mark


  3. Volume of gas at anode : volume of gas at cathode = 1 : 2. The volume of hydrogen is twice that of oxygen.

    ½ mark

  4. (ii) White silver chloride turns grey in sunlight because silver metal is formed:

    ½ mark

  5. This is a decomposition reaction (photolytic decomposition).

    ½ mark

Answer: (i) To increase conductivity; H₂ at cathode, O₂ at anode; anode : cathode volume = 1 : 2. (ii) White AgCl turns grey; photolytic decomposition.

Where the marks are

  • Acid increases conductivity of water (½ mark)
  • Hydrogen at cathode (½ mark)
  • Oxygen at anode (½ mark)
  • Volume ratio anode : cathode = 1 : 2 (½ mark)
  • AgCl turns grey (½ mark)
  • Photolytic decomposition reaction (½ mark)

Revise the chapter

Practise this chapterBoard-style questions from Chemical Reactions and Equations, one at a time, marked against the answer key and marking points.Back to the full paper2023 board paper, set 31/4/1: every question, by section.

The question is transcribed from the official paper; figures are described in words. The solution, hints and chapter tag are ours. Spotted an error? Write tosupport@questionbuddy.in.