The following experimental rate data were obtained for a reaction carried out at 25 °C : A(g) + B(g) → C(g) + D(g) Initial [A(g)]/mol dm⁻³ Initial [B(g)]/mol dm⁻³ Initial rate/mol dm⁻³ s⁻¹ --- --- --- 3.0 × 10^-2 2.0 × 10^-2 1.89 × 10^-4 3.0 × 10^-2 4.0 × 10^-2 1.89 × 10^-4 6.0 × 10^-2 4.0 × 10^-2 7.56 × 10^-4 What are the orders with respect to A(g) and B(g) ? (A) Order w.r.t. A: Zero; Order w.r.t. B: Second (B) Order w.r.t. A: First; Order w.r.t. B: Zero (C) Order w.r.t. A: Second; Order w.r.t. B: Zero (D) Order w.r.t. A: Second; Order w.r.t. B: First

ChemistryCBSE Class 12 · Board exam 2023, set 56/5/1 · 1 mark · MCQ

CBSE Class 12 Chemistry 2023: question 13

Set in the CBSE Class 12 board exam of 2023, paper 56/5/1, section A, question 13, for 1 mark. Try it first; the hints and our step-by-step solution are below.

Q13 · 1 mark · MCQChemical Kinetics

The following experimental rate data were obtained for a reaction carried out at 25 °C :
$A_{(g)} + B_{(g)} \to C_{(g)} + D_{(g)}$

Initial [A(g)]/mol dm⁻³	Initial [B(g)]/mol dm⁻³	Initial rate/mol dm⁻³ s⁻¹
$3.0 \times 1 0^{- 2}$	$2.0 \times 1 0^{- 2}$	$1.89 \times 1 0^{- 4}$
$3.0 \times 1 0^{- 2}$	$4.0 \times 1 0^{- 2}$	$1.89 \times 1 0^{- 4}$
$6.0 \times 1 0^{- 2}$	$4.0 \times 1 0^{- 2}$	$7.56 \times 1 0^{- 4}$

What are the orders with respect to A(g) and B(g) ?

(A)Order w.r.t. A: Zero; Order w.r.t. B: Second
(B)Order w.r.t. A: First; Order w.r.t. B: Zero
(C)Order w.r.t. A: Second; Order w.r.t. B: Zero
(D)Order w.r.t. A: Second; Order w.r.t. B: First

Source: official question paper from cbse.gov.in (PDF). See it in the full 2023 board paper, set 56/5/1.

Hints

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

Hint 1

Compare experiments in which only one concentration changes.

Hint 2

Use $2^{n} =$ the ratio of the rates.

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.

Experiments 1 and 2: doubling [B] leaves the rate unchanged, so the order w.r.t. B is 0.
Experiments 2 and 3: doubling [A] increases the rate 4 times, so the order w.r.t. A is 2.
1 mark

Answer: (C) A second, B zero

Where the marks are

Deduces order 2 in A and 0 in B (1 mark)

Revise the chapter

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

Practise this chapterBoard-style questions from Chemical Kinetics, one at a time, marked against the answer key and marking points.Back to the full paper2023 board paper, set 56/5/1: every question, by section.

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CBSE Class 12 Chemistry 2023: question 13

Hints

Step-by-step solution

Revise the chapter

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