For the decompoistion of phosphorus pentachloride at `200^(@)C`, it is observed that its pressure falls form `0.15` to `0.10 atm` in `25 min`. Calculate the average rate of reaction in
(a) `atm min^(-1)` , (b) `mol L^(-1) s^(-1)`

Explanation

(a) `Rate = ("Pressure change")/("Time")`
`= (0.15 atm-0.10)/(25 min)`
`= (0.05 atm)/(25 min) = 0.002 atm min^(-1)`
(b) `PV = nRT, T = 273 + 200^(@)C = 473 K`
`(Delta(n//V))/(Delta t) mol L^(-1) min^(-1) = (Delta P)/(Delta t) xx (1)/(RT)`
`= (0.002 atm min^(-1))/((0.082 L -atm K^(-1) mol^(-1))(473 K))`
`= 5.15 xx 10^(-5) mol L^(-1) min^(-1)`
`= 8.58 xx 10^(-7) mol L^(-1) s^(-1)`