A manometer attached to a flask contains with ammonia gas have no difference in mercury level initially as shown in diagram. After sparking into the flask, ammonia is partially dissociated as `2NH_(3)" (g)"rarr N_(2)" (g)"+3H_(2)" (g)"` now it have difference of 6 cm in mercury level in two columns, what is partial pressure of `H_(2)" (g)"` at equilibrium?

Options

A. 18 cm Hg
B. 9 cm Hg
C. 27 cm Hg
D. 24 cm Hg

Answer

C

Explanation

`{:(,2NH_(3) (g),hArr,N_(2) (g) ,+ 3H_(2) (g)),(t_(0),76,,0," "0),(t_(eq),76 - 2x,,x," "3x):}`
Total pressure after dissociation `= 76 - 2x + x + 3 x = 76 + 2x`
`:.` Increase in pressure `= 2x = 18`
`x = 9 cm`
Partial pressure of `H_(2) = 3 x = 27 cm`