A mixture of nitrogen and hydrogen in the ratio of `1: 3` reach equilibrium with ammonia, when `50 %` of the mixture has reacted. If the total pressure is `P`, the partial pressure of ammonia in the equilibrium mixture was :

Options

A. `P//2`
B. `P//3`
C. `P//4`
D. `P//6`

Answer

B

Explanation

`{:(,N_(2),+,3 H_(2),hArr,2 NH_(3)),("Intial",1 " mole",,3 "moles",,0),("At eqm." ,1-x,,3-3x,,2 x):}`
But out of 4 moles of the mixture , 2 moles have reacted and hence 2 moles are left .
` :. (1-x) + ( 3-3x) = 2 or 4 x = 2 or 4 x = 2 or x = 0.5`
` :. " Total moles at equilibrium " `
` = (1-x) + (3-3x )+ 2 x `
` = 4 - 2 x = 4 - 1 = 3 `
No . of moles of `NH_(3)` at equilibrium = 2 x = 1
` :. p_(NH_(3)) = 1/3 xx P = P/3 `