Question #f5a83

1 Answer
Aug 24, 2017

0.303 atm.


Given the reaction, write the mass action expression using the partial pressures of each gas:

KP=PH2,eqPS,eqPH2S,eq=0.833

All the coefficients were 1 so there are no exponents to worry about. We know that PH2S,i=0.163 atm. An ICE table gives:

H2S(g) H2(g)+S(g)

I 0.163 0 0
C x +x +x
E 0.163x x x

We define x as the partial pressure of H2(g) or S(g) at equilibrium, i.e. PH2,eq=PS,eq.

This becomes:

0.833=x20.163x

The KP is not small, so we'll have to solve this quadratic equation in full.

0.833(0.163x)x2=0

You should get:

xPH2,eq=PS,eq=0.140 atm

This says that H2S decomposes almost completely, as PH2S,eq=0.023 atm.

Ptot=P1+P2+...

=(0.163x)+(x)+(x)

=0.163+x

=0.163 atm+0.140 atm

= 0.303 atm