Question

A chemical system within a sealed 1 L reaction vessel is described by the following reversible reaction equation:
2H2S(g) <-->2H2(g) + S2(g)
If the equilibrium constant is 0.000 004 200 at 1103 K find:
the reaction quotient initially.

Answer 1

This makes no sense to me. Reaction quotients are determined by substituting non-equilibrium concns. With a Keq of 4.2E-6 (I assume that is what you meant) we can calculate the equilibrium concns of the three species. I don't see any numbers with which to calculate Qrxn.

Answer 2

how I would answer this is to say that though we cannot determine the amount of moles, we can make a few assumptions, primarily that because it is the initial reaction the products have not been formed and the reaction consists of only reactants. As such our Qc equation will have a value of 0 which is valid as it is not a negative value.