The reaction `XrarrY` (Product ) follows first order kinetics. In 40 minutes, the concentration of X changes from 0.1M to 0.025 M , then rate of reaction when concentration of X is `0.01`M is :

Options

A. `1.73xx10^(-4)M min ^(-1)`
B. `3.47xx10^(-5) M min ^(-1)`
C. `3.47xx10^(-4)M min ^(-1)`
D. `1.73xx10^(-5)M min ^(-1)`

Answer

C

Explanation

since the concentration of 'X' changes from 0.1 M to 0.025 I .e., it becomes 1/4 or it is equal to two times `t_(1//2)`) in 40 minutes
`therefore 2 xxt _(1//2) = 40 min or t_(1//2) = 40//2=20 min.`
`r= K[X] = (0.693)/(t) xx0.01 =(0.693)/(t)xx0.01 =(0.693)/(20)xx0.01`
` = 3.465xx10^(-4) M min^(-1)`