JEE Main · 2026 · 02 Apr 2026 · Shift 1 · Chemical Kinetics

t_{100%}

is the time required for the

100%

completion of the reaction while

t_{1/2}

is the time required for

50%

of the reaction to be completed. Which of the following option correctly represents the relation between

t_{100%}

and

t_{1/2}

for zero and first order reactions respectively?

Answer: (B)

Solution

For a zero-order reaction

[A] = [A]_{0} - k t

, so complete consumption needs

t_{100%} = \frac{[ A ] _{0}}{k}

while

t_{1/2} = \frac{[ A ] _{0}}{2 k}

; hence

t_{100%} = 2 t_{1/2}

. For a first-order reaction the concentration falls to zero only asymptotically, so

t_{100%}

is infinite, written symbolically as

(t_{1/2})^{\infty}

JEE Main · 2026 · 02 Apr 2026 · Shift 1 · Single correct option