Question

In which direction does the reaction proceed to reach equilibrium? The reaction will proceed from right to left to reach equilibrium. The reaction will proceed from left to right to reach equilibrium.

The first step in the industrial synthesis of hydrogen is the reaction of steam and methane to give synthesis gas, a mixture of carbon monoxide and hydrogen.

H2O(g)+CH4(g)⇌CO(g)+3H2(g) Kc = 4.7 at 1400K. A mixture of reactants and products at 1400K contains 0.035 M H2O, 0.050M CH4, 0.15 M CO, and 0.20 M H2.

In which direction does the reaction proceed to reach equilibrium?

The reaction will proceed from right to left to reach equilibrium.

OR

The reaction will proceed from left to right to reach equilibrium.

The problem is from Mastering Chemistry. I'm not sure how to approach or solve this problem.

Answer 1

Surely it will be from left to right as written....? (That is our left to our right as we view the page or the screen).

Explanation:

You got the reaction....

`CH_4(g) + H_2O(g) rightleftharpoons CO(g) + 3H_2(g)`

Now at equilibrium the RATE of the forward reaction is EQUIVALENT to the RATE of the backward reaction. And this is what the condition of equilibrium specifies. However, we started with (superheated) steam and methane, and it should proceed from LEFT to right.

Anyway, we should put some noombers in....

We know, `K_"eq"=([H_2(g)]^3[CO(g)])/([CH_4(g)][H_2O(g)])=4.7`

And we can calculate the reaction quotient `Q_"rxn quotient"` with the starting concentrations (and of course here these INITIAL, STARTING concentrations do NOT express the equilibrium concentrations)......

`Q_"rxn quotient"=([H_2(g)]^3[CO(g)])/([CH_4(g)][H_2O(g)])=((0.20)^3xx0.15)/(0.050xx0.035)=0.686`

And since `Q` IS LESS than `K_(eq)`...the equilibrium will move in the FORWARD direction to INCREASE the concentrations of the products, and DECREASE the concentrations of reactants until such time as `Q=K_"eq"`, at which time the reaction has reached equilibrium.

And note that the condition of equilibrium specifies EQUALITY of forward and reverse rates of reaction.