The gaseous decomposition reaction, `A(g) rarr 2B(g) + C(g)` is observed to first order over the excess of liquid water at `25^(@)` C. It is found that after 10 minutes the total pressure of system is 188 torr and after very long time it is 388 torn The rate constant of the reaction (in `hr^(1)`) is: [Given: vapour pressure of `H_(2)` O at `25^(@)` C is 28 torr(In 2 = 0.7, In 3 = 1.1, In 10 = 2.3)]

Options

A. 0.02
B. 1.2
C. 0.2
D. 2.2

Answer

B

Explanation

Let initial pressure `A(g) rarr2B(g) +C(g)`
`P_(0) 0 0`
After 10 min `(P_(0)-x) 2x x`
as per given `(P_(0)-x)+2x+x+` vapour pressure of `H_(2)O=188`
`P_(0)+2x=160` and `3P_(0)+28=388` so `P_(0)=120` and `x =20` torr
`0.02 min^(-1) =1.2 hr^(-1)`