Problem

Two substances A (

t_{1/2} = 5 \text{ min}

) and B (

t_{1/2} = 15 \text{ min}

) are taken in such a way that initially

[\text{A}] = 4[\text{B}]

. The time after which both the concentration will be equal is: (Assume that both reactions are first order) (a)

5 \text{ min}

(b)

15 \text{ min}

(c)

20 \text{ min}

(d) Concentration can never be equal