Equimolar concentrations of `H_(2)` and `I_(2)` are heated to equilibrium in a 2 L flask. At equilibrium, the forward and backward rate constants are found to be equal. What percentage of initial concentration of `H_(2)` has reached at equilibrium ?

Options

A. `33 %`
B. `66 %`
C. `50%`
D. `40%`

Answer

C

Explanation

`{:(,H_(2)(g),+,I_(2) (g),hArr,2 HI(g)), (" Intial",1 "mol",,1 "mol",,0),("At eqm.",1-x,,1-x,,2x),("Molar conc.",(1-x)/2,,(1-x)/2,,(2x)/2"mol"L^(-1)),(,,,,,=x):}`
` K= (x^(2))/((1-x)/2 xx (1-x)/2 )=(4 x^(2))/(1-x)^(2) approx4x^(2)`
But `K= (k_(f))/(k_(b))=1`
`:. 4"" x^(2)=1 or x^(2) = 1//4 or x = 1//2 , i.e., 50%`