The correct balanced chemical equation showing exothermic reaction in which natural gas burns in air is : (A) CH_4 + O_2 → CO_2 + 2H_2O (B) CH_4 + 2O_2 → 2CO_2 + 2H_2O + Energy (C) CH_4 + 2O_2 → CO_2 + 2H_2O (D) CH_4 + 2O_2 → CO_2 + 2H_2O + Energy

(D) CH_4 + 2O_2 → CO_2 + 2H_2O + Energy

ScienceCBSE Class 10 · Board exam 2025, set 31/2/1 · 1 mark · MCQ

CBSE Class 10 Science 2025: question 1

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

Q1 · 1 mark · MCQChemical Reactions and Equations

The correct balanced chemical equation showing exothermic reaction in which natural gas burns in air is :

(A) $C H_{4} + O_{2} \to C O_{2} + 2 H_{2} O$
(B) $C H_{4} + 2 O_{2} \to 2C O_{2} + 2 H_{2} O + Energy$
(C) $C H_{4} + 2 O_{2} \to C O_{2} + 2 H_{2} O$
(D) $C H_{4} + 2 O_{2} \to C O_{2} + 2 H_{2} O + Energy$

Source: official question paper from cbse.gov.in (PDF). See it in the full 2025 board paper, set 31/2/1.

Hints

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

Hint 1

Natural gas is methane. What must an equation show for an exothermic reaction?

Hint 2

Count the C, H and O atoms on both sides of each option, and look for the word 'Energy'.

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.

Natural gas is mainly methane, $C H_{4}$ . Burning it in air gives carbon dioxide and water, and heat is given out, so the reaction is exothermic.
Check the balance. Left side: 1 C, 4 H, 4 O. Right side of $C H_{4} + 2 O_{2} \to C O_{2} + 2 H_{2} O$ : 1 C, 4 H, $2 + 2 = 4$ O. So it is balanced.
(A) is unbalanced. (B) has $2 C O_{2}$ , which gives 2 C on the right, so it is wrong. (C) is balanced but does not show the energy released. Only (D) is balanced and shows the energy, so the answer is (D).
1 mark

Answer: (D) $C H_{4} + 2 O_{2} \to C O_{2} + 2 H_{2} O + Energy$

Where the marks are

Chooses option (D), the balanced equation that shows energy released (1 mark)

Revise the chapter

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

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 paper2025 board paper, set 31/2/1: every question, by section.

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CBSE Class 10 Science 2025: question 1

Hints

Step-by-step solution

Revise the chapter

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