The gas arsine, ash3, decomposes as follows. 2 ash3(g) equilibrium reaction arrow 2 as(s) + 3 h2(g) in an experiment at a certain temperature, pure ash3(g) was placed in an empty, rigid, sealed flask at a pressure of 392.0 torr. after 48 hours the pressure in the flask was observed to be constant at 488.0 torr. (a) calculate the equilibrium pressure of h2(g).

Answer : The equilibrium pressure of is, 288 torr

Explanation :  Given,

Initial pressure of = 392.0 torr

Total pressure = 488.0 torr

The balanced equilibrium reaction is,

Initial pressure     392.0                            0

At eqm.               (392.0-2p)                     (3p)

The expression of equilibrium constant for the reaction will be:

As,

Total pressure at equilibrium =  (392.0-2p) + (3p)  = 488.0 torr

(392.0-2p) + (3p)  = 488.0

392.0 + p = 488.0

p = 488.0 - 392.0

p = 96

Thus, the equilibrium pressure of = 3p = 3(96) = 288 torr

Therefore, the equilibrium pressure of is, 288 torr