For 2A + B to text products : doubling both [A] and [B] increases rate from 0.3 to 2.4 text mol L ^ -1 text s ^ -1 ; doubling [A] alone increases rate from 0.3 to 0.6 text mol L ^ -1 text s ^ -1 . Which statement is correct?

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EEJ MAIN Chemistry QUESTION #5530

Question 1

For $2A + B \to \text{products}$: doubling both [A] and [B] increases rate from $0.3$ to $2.4\ \text{mol L}^{-1}\text{s}^{-1}$; doubling [A] alone increases rate from $0.3$ to $0.6\ \text{mol L}^{-1}\text{s}^{-1}$. Which statement is correct?

Total order of the reaction is 4
Order w.r.t. B is 2✔️
Order w.r.t. B is 1
Order w.r.t. A is 2

Correct Answer Explanation

When only [A] doubles: rate doubles → order w.r.t. A = 1. When both [A] and [B] double: rate increases 8-fold ($2.4/0.3 = 8$). Effect of doubling both: $2^1 \times 2^n = 8 \Rightarrow 2^{1+n} = 8 = 2^3 \Rightarrow 1+n = 3 \Rightarrow n = 2$. Order w.r.t. B = 2. Total order = 1 + 2 = 3.

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