A sample of `HI(g)` is placed in flask at a pressure of `0.2 atm`. At equilibrium. The partial pressure of `HI(g)` is `0.04 atm`. What is `K_(p)` for the given equilibrium?
`2HI(g) hArr H_(2)(g)+I_(2)(g)`

Explanation

Given: Pressure of `HI=0.2atm` (initially),
Pressure of `HI=0.04atm` (equilibrium)
`2HI(g)harrH_(2)(g) + l_(2)(g)`
`{:(,2HI(g),hArr,H_(2)(g),+,I_(2)(g)),("Initial pressure",0.2 atm,,0,+,0),("At eqm.",0.04,,0.16/2 atm,,0.16/2 atm):}`
`=0.08atm=0.008atm`
(Decrease in the pressure of `HI=0.2-0.04=0.16atm`)
Formulae `thereforeK_(P)= (P_(H_(2)xxP_(1_(2))))/(P_(HI)^(2))`
Substitution & Calculation: ` (0.08atmxx0.08atm)/((0.04atm)^(2))=4.0`