A 0.15 mol sample of H2S is placed in a10 L reaction vessel and heated to 1132◦C. At equilibrium, 0.03 mol H2is present. Calculate the value of Kc for the reaction2 H2S(g)⇀↽2 H2(g) + S2(g)at 1132◦C.

Answer 1

0.15 mols/10 L = 0.015 mols/L = 0.015 M
0.03 mols/10 L = 0.003 M
...............2H2S(g)⇀↽ 2H2(g) + S2(g)
I..................0.015...........0..............0
C.................-2x.............2x...............x
E................0.015-2x......2x...............x
But the problem tells you (H2) at equilibrium is 0.003. Therefore, use that to evaluate x, (from 0.015-2x =0.003) then 2x, then place those numbers into the Kc expression and solve for Kc. Post your work if you get stuck.