ScienceCBSE Class 10 · Board exam 2023, set 31/4/1 · 1 mark · MCQ

CBSE Class 10 Science 2023: question 2

Set in the CBSE Class 10 board exam of 2023, paper 31/4/1, section A, question 2, for 1 mark. Try it first; the hints and our step-by-step solution are below.

Q2 · 1 mark · MCQChemical Reactions and Equations

When aqueous solutions of potassium iodide and lead nitrate are mixed, an insoluble substance separates out. The chemical equation for the reaction involved is :

(A) $KI + PbN O_{3} \to PbI + KN O_{3}$
(B) $2KI + Pb (N O_{3})_{2} \to Pb I_{2} + 2KN O_{3}$
(C) $KI + Pb (N O_{3})_{2} \to PbI + KN O_{3}$
(D) $KI + PbN O_{3} \to Pb I_{2} + KN O_{3}$

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

Check the valency of lead and write the correct formulae first.

Hint 2

Then balance the K and I atoms.

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.

Lead is +2, so lead nitrate is $Pb (N O_{3})_{2}$ and lead iodide is $Pb I_{2}$ .
The balanced equation is $2KI + Pb (N O_{3})_{2} \to Pb I_{2} ↓ + 2KN O_{3}$ , so option (B) is correct. Yellow $Pb I_{2}$ precipitates.
1 mark

Answer: Option (B)

Where the marks are

Correct balanced equation with Pb(NO3)2 and PbI2, option (B) (1 mark)

Revise the chapter

Chapter: Chemical Reactions and Equations (notes, formulas, where marks are lost and every past question)

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.

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CBSE Class 10 Science 2023: question 2

Hints

Step-by-step solution

Revise the chapter

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