JEE Advanced · 2013 · 02 Jun 2013 · Paper 1 · Chemical Kinetics

In the reaction,

P + Q ⟶ R + S

the time taken for 75% reaction of

P

is twice the time taken for 50% reaction of

P

. The concentration of

Q

varies with reaction time as shown in the figure. The overall order of the reaction is

(A)2
(B)3
(C)0
(D)1✓ Correct

Answer: (D)

Solution

For reactant P: For a first-order reaction,

t_{75%} = 2 \times t_{50%}

(since

t_{75%} = 2 t_{1/2}

). This confirms P follows first-order kinetics.

For reactant Q: The graph shows concentration of Q decreasing linearly with time, which is characteristic of zero-order kinetics.

Overall order = order w.r.t. P + order w.r.t. Q = 1 + 0 = 1

JEE Advanced · 2013 · 02 Jun 2013 · Paper 1 · Single correct option

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