Consider the following equilibrium process at 700°C:

2H2 + S2 ↔ 2H2S

Analysis shows that there are 2.50 moles of H2, 1.35x10^-5 mole of S2, and 8.70 moles of H2S present in a 12.0-L flask. Calculate the equilibrium constant Kc for the reaction.

1.08*10^7

The equilibrium constant can be calculated by: Kc= [product]/[reactants].

Before you know the exact concentration variables necessary to do this you need to calculate the moles present in your reaction. In the example you provided the moles per liter are:
H2S= 8.7M/12.0L= 0.73 moles
H2= 2.5M/12.0 L= 0.21 moles
S2= (1.35 x 10^-5M)/12.0L= 1.13 x 10^-6
Now that you have the exact proportions of moles are are able to insert these variables into the above equation:
Kc= [product]/[reactants]=[0.73]^2/[0.21]^2[1.13 x 10^-6]=9.3 x 10^6
Remember during calculations that you need to place your coefficient from the reaction into the exponent of your Kc equation. That is why I took [0.73]^2 rather than just leaving it at [0.73]. This Kc tells us that the reaction is shifted to the right and we have a high proportion of hydrogen sulfide in this reaction when equilibrium is achieved.

ASSUMING that the moles indicated are present at equilibrium, then calculate concns of each by mole/L, then plug into the Keq experession. If you need more assistance, please explain what you don't understand about the procedure. Frankly, the numbers don't look right to me but I may have overlooked something.

Well, it seems we have a "che-mystery" on our hands! To calculate the equilibrium constant Kc, we need to use the formula:

Kc = ([H2S]^2) / ([H2]^2[S2])

Now, let's substitute the given values into the equation:

Kc = (8.70^2) / (2.50^2 x 1.35x10^-5)

Before we crunch the numbers, I must applaud you for your precise measurements. Now, let's calculate Kc:

Kc ≈ 8.70^2 / (2.50^2 x 1.35x10^-5)

Kc ≈ 75.92 / (6.25 x 1.8225x10^-10)

Kc ≈ 75.92 / 1.1415625x10^-9

Kc ≈ 6.648116x10^16

So, my dear friend, Kc is approximately 6.648116x10^16. But remember, this value tells us more about the equilibrium position rather than entertaining us at parties.

To calculate the equilibrium constant (Kc) for the given reaction, you need to use the concentrations of the reactants and products at equilibrium. The equilibrium constant expression for this reaction is:

Kc = [H2S]^2 / ([H2]^2 [S2])

Given that there are 2.50 moles of H2, 1.35x10^-5 mole of S2, and 8.70 moles of H2S in a 12.0-L flask, we need to calculate the concentrations of each species.

Concentration (in moles per liter) can be calculated using the formula:

Concentration = (number of moles) / (volume in liters)

Concentration of H2: 2.50 moles / 12.0 L = 0.2083 M
Concentration of S2: 1.35x10^-5 moles / 12.0 L = 1.13x10^-6 M
Concentration of H2S: 8.70 moles / 12.0 L = 0.725 M

Now, substitute these concentrations into the equilibrium constant expression and calculate Kc:

Kc = (0.725 M)^2 / ((0.2083 M)^2 (1.13x10^-6 M))

Kc ≈ 8.321x10^9

Therefore, the equilibrium constant (Kc) for the reaction is approximately 8.321x10^9.

Thinking critically An analysis for copper was performed on two pure solids. One solid was found to contain 43.0% copper. Could these solids be samples of the same copper-containing compound? Explain your answer.