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What is observed when… (Class 10 Science 2023, Q21a)

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ScienceCBSE Class 10 · Board exam 2023, set 31/2/1 · 2 marks · Very short answer

CBSE Class 10 Science 2023: question 21(a)

Set in the CBSE Class 10 board exam of 2023, paper 31/2/1, section B, question 21(a), for 2 marks. Try it first; the hints and our step-by-step solution are below.

Q21(a) · 2 marks · Very short answerChemical Reactions and Equations

What is observed when aqueous solutions of potassium iodide and lead nitrate are mixed together ? Name the type of reaction and write the chemical equation for the reaction that occurs.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2023 board paper, set 31/2/1.

Hints

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

Hint 1

Think about which product of the ion exchange is insoluble in water and what colour it is.

Hint 2

When two compounds swap their ions, what is that type of reaction called?

Hint 3

The products are lead iodide and potassium nitrate. Balance the iodide and nitrate ions.

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. Observation: A yellow precipitate forms as soon as the two colourless solutions are mixed. This precipitate is lead iodide, .

    ½ mark

  2. Type of reaction: This is a double displacement reaction, and because an insoluble solid forms it is also a precipitation reaction. The two compounds exchange their ions.

    ½ mark

  3. Balanced equation:

    1 mark

Answer: Yellow precipitate of PbI₂; double displacement (precipitation) reaction; Pb(NO₃)₂ + 2KI → PbI₂ + 2KNO₃

Where the marks are

  • States that a yellow precipitate of lead iodide forms (½ mark)
  • Names the reaction as double displacement or precipitation (½ mark)
  • Writes the correct balanced equation (1 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 31/2/1: 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.