The products formed when Aluminium and Magnesium are burnt in the presence of air respectively are : (A) Al_3O_4 and MgO_2 (B) Al_2O_3 and MgO (C) Al_3O_4 and MgO (D) Al_2O_3 and MgO_2

ScienceCBSE Class 10 · Board exam 2025, set 31/1/1 · 1 mark · MCQ

CBSE Class 10 Science 2025: question 2

Set in the CBSE Class 10 board exam of 2025, paper 31/1/1, section A, question 2, for 1 mark. Try it first; the hints and our step-by-step solution are below.

Q2 · 1 mark · MCQMetals and Non-metals

The products formed when Aluminium and Magnesium are burnt in the presence of air respectively are :

(A) $A l_{3} O_{4}$ and $Mg O_{2}$
(B) $A l_{2} O_{3}$ and $MgO$
(C) $A l_{3} O_{4}$ and $MgO$
(D) $A l_{2} O_{3}$ and $Mg O_{2}$

Source: official question paper from cbse.gov.in (PDF). See it in the full 2025 board paper, set 31/1/1.

Hints

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

Hint 1

Use the valencies of Al (3), Mg (2) and O (2).

Hint 2

Cross the valencies to get each oxide's formula.

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.

Al has valency 3 and O has valency 2. Crossing the valencies gives $A l_{2} O_{3}$ : $4 Al + 3 O_{2} \to 2 A l_{2} O_{3}$
Mg has valency 2, so its oxide is $MgO$ : $2 Mg + O_{2} \to 2 MgO$ . The answer is option (B).
1 mark

Answer: Al₂O₃ and MgO, option (B)

Where the marks are

Chooses option (B) (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 paper2025 board paper, set 31/1/1: every question, by section.

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CBSE Class 10 Science 2025: question 2

Hints

Step-by-step solution

Revise the chapter

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