Question

For a reaction A + B → P which of the following conditions provides highest rates, if the order of the reaction with respect to A & B are two & one respectively :-

• A. One mole of A + One mole of B in one litre vessel
• B. 0.2 mole of A + 0.2 mole of B in 0.1 litre vessel
• C. 2 mole of A+ 2 mole of B in 2 litre vessel
• D. 0.5 mole of A+ 0.5 mole of B in 0.5 litre vessel

Answer 1

Answer: (B)

Option (B)

Answer 2

Working:
The rate law is
Rate = k [A]²[B].

Calculate concentrations:

• (A): [A] = 1 M, [B] = 1 M → Rate ∝ 1²×1 = 1
• (B): [A] = 0.2/0.1 = 2 M, [B] = 2 M → Rate ∝ 2²×2 = 8
• (C): [A] = 2/2 = 1 M, [B] = 1 M → Rate ∝ 1
• (D): [A] = 0.5/0.5 = 1 M, [B] = 1 M → Rate ∝ 1

Clearly, the highest rate is in (B).