A The initial concentrations of the reactants are [H₂]_i = [CO₂]_i = 0.0150 M. Just as before, we will focus on the change in the concentrations of the various substances between the initial and final states. If we define the change in the concentration of H₂O as x, then ?[H₂O] = +x. We can use the stoichiometry of the reaction to express the changes in the concentrations of the other substances in terms of x. For example, 1 mol of CO is produced for every 1 mol of H₂O, so the change in the CO concentration can be expressed as ?[CO] = +x. Similarly, for every 1 mol of H₂O produced, 1 mol each of H₂ and CO₂ are consumed, so the change in the concentration of the reactants is ?[H₂] = ?[CO₂] = ?x. We enter the values in the following table and calculate the final concentrations.

H2(g)+CO2(g)?H2O(g)+CO(g)
	[H2]	[CO2]	[H2O]	[CO]
initial	0.0150	0.0150	0	0
change	?x	?x	+x	+x
final	(0.0150 ? x)	(0.0150 ? x)	x	x

B We can now use the equilibrium equation and the given K to solve for x:

To two significant figures, this K is the same as the value given in the problem, so our answer is confirmed.