Equilibrium constant for the following equilibrium is given at `)^(@)C` . `Na_(2)HPO_(4)` . `12H_(2)O(s) hArrNa_(2)HPO_(4)` . `7H_(2)O(s) + 5H_(2)O(g)` `K_(p) = 31.25xx10^(-13)`. At equilibrium what will be partial pressure of water vapour:

Options

A. `(1)/(5)xx10^(-3)` atm
B. `0.5xx10^(-3)` atm
C. `5xx10^(-2)` atm
D. `5xx10^(-3)` atm

Answer

D

Explanation

`Na_(2)HPO_(4)` . `12H_(2)O(s)hArrNa_(2)HPO_(4).7H_(2)O(s)+5H_(2)O(g)`
`K_(p) = 31.25xx10^(-13)`
`K_(p) = (P_(H_(2)O))^(5)`
`(P_(H_(2)O))^(5) =31.25xx10-13`
`(P_(H_(2)O)) =(3125)^(1//5)xx(10^(-15))^(1//5)`
`(P_(H_(2)O)) =5xx10^(-3)`