Textbook 5I.11

[Shujing Guo 1E]

The problem statement:
A reaction vessel of volume 0.500L at 700 K contains 1.20 mmol SO2(g), 0.50mmol O2(g), and 0.10mmol SO3(g). At 700K, Kc = 1.7*10^6 for the equilibrium 2SO2(g) + O2(g) <-> 2SO3(g). calculate the reaction quotient Qc. Will more SO3(g) tend to form?

Can someone walk me through how to calculate Qc? I thought we just take (0.1)^2 divided by (1.2)^2*(0.5)
Thank you!

[Ava Vehemente 3D]

Hi! For this question, you have to pay attention to the units. The prompt gives the concentrations of the reactants and products in mmol, but when calculation the equilibrium constant or reaction quotient, the concentrations must be in mol/L. So, first you should convert mmol to mol by multiplying all of the given values by 10^-3. Then, divide each value by 0.500 L so that all of the units are in mol/L. These values are the ones that you will use for Q = [S03]^2/([SO2]^2[O2]).

[505736451]

After you calculate the reaction quotient, you then compare Q to k. If Q<k, then products are favored and more SO3 will form. If Q>k, then reactants are favored and less SO3 is formed.