ScienceCBSE Class 10 · Board exam 2026, set 31/4/1 · 3 marks · Short answer

CBSE Class 10 Science 2026: question 27(B)

Set in the CBSE Class 10 board exam of 2026, paper 31/4/1, section B, question 27(B), for 3 marks. Try it first; the hints and our step-by-step solution are below.

Q27(B) · 3 marks · Short answerMetals and Non-metals

(i) Write all the reactions involved in the extraction of Zn from ZnS.
(ii) Hydrogen gas is not evolved when most of the metals react with nitric acid. Give reason.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2026 board paper, set 31/4/1.

Hints

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

Hint 1

A sulphide ore must first be changed into an oxide. Which process does that?

Hint 2

Which common reducing agent turns ZnO into Zn?

Hint 3

Think about what nitric acid does to H $_{2}$ as soon as it forms.

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.

(i) Roasting: Zinc blende is heated strongly in excess air, giving zinc oxide:
$2 Z n S (s) + 3 O_{2} (g) heat 2 Z n O (s) + 2 S O_{2} (g)$
1 mark
Reduction: Zinc oxide is reduced with carbon to give zinc metal:
$Z n O (s) + C (s) heat Z n (s) + C O (g)$
1 mark
(ii) Nitric acid is a strong oxidising agent. It oxidises the hydrogen produced to water and is itself reduced to oxides of nitrogen ( $N_{2} O$ , $N O$ , $N O_{2}$ ). So hydrogen gas is not evolved (except with Mg and Mn and very dilute HNO $_{3}$ ).
1 mark

Answer: (i) $2 Z n S + 3 O_{2} \to 2 Z n O + 2 S O_{2}$ ; $Z n O + C \to Z n + C O$ . (ii) HNO $_{3}$ is a strong oxidising agent and oxidises the H $_{2}$ formed to water.

Where the marks are

Writes the balanced roasting equation (1 mark)
Writes the reduction of ZnO with carbon (1 mark)
States that HNO $_{3}$ is a strong oxidising agent that oxidises H $_{2}$ to water (1 mark)

Revise the chapter

Chapter: Metals and Non-metals (notes, formulas, where marks are lost and every past question)

Practise this chapterBoard-style questions from Metals and Non-metals, one at a time, marked against the answer key and marking points.Back to the full paper2026 board paper, set 31/4/1: every question, by section.

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CBSE Class 10 Science 2026: question 27(B)

Hints

Step-by-step solution

Revise the chapter

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