Hydrogen sulfide gas decomposes to form gaseous hydrogen and sulfur according to the following equation: 2 H2S(g) ⇌ 2 H2(g) + S2(g), Kc = 1.67 x 10-7
Shortly after lab scientists stressed the system, the following non-equilibrium concentration values were measured and recorded:
[H2S] = 0.0750 M, [H2] = 0.0525 M, [S2] = 0.0325 M

a. What is the reaction quotient, Q?
b. In which direction will the reaction proceed?

The  concentration of H2 at equilibrium = 2X = 0.001659 M

Explanation:

2 H2S(g) ⇔ 2 H2(g) + S2(g)

This means that for 2 moles of H2S consumed there is produced 2 moles of H2 and 1 mole S2

Step 2: Given data

0.47 moles of a gas H2S is placed in a 3L container.

Kc = 9.3 * 10^-8 (this at 400 °C)

Step 3: Calculate initial concentration of H2S

Molarity of H2S = moles of H2S / volume of H2S

Molarity of H2S = 0.47 moles / 3L

Molarity of H2S = 0.1567 M

Step 4: The initial concentration of H2S is 0.1567 M

The initial concentration of H2 and S2 is 0M

There will react 2X of H2S, that means there will be also produced 2X of H2 and X of S2 ( Since the ratio is 2:2:1).

The final concentration of H2S is 0.1567 - 2X

The final concentration of H2 is 2X

The final concentration of S2 is X

Step 5: Write the Kc

Kc =9.3 * 10^-8 =  ([S2]*[H2]² )/ [H2S]²

Kc = 9.3 * 10^-8 = X *(2X)² / (0.1567 - 2X)²

4X³ = 0.1567²X * 9.3*10^-8

if we calculate X = 0.000829571

The concentration of S2 at equilibrium = X = 0.000829571 M

The  concentration of H2 at equilibrium = 2X = 0.001659 M2 H2S(g) ⇔ 2 H2(g) + S2(g)

This means that for 2 moles of H2S consumed there is produced 2 moles of H2 and 1 mole S2

Step 2: Given data

0.47 moles of a gas H2S is placed in a 3L container.

Kc = 9.3 * 10^-8 (this at 400 °C)

Step 3: Calculate initial concentration of H2S

Molarity of H2S = moles of H2S / volume of H2S

Molarity of H2S = 0.47 moles / 3L

Molarity of H2S = 0.1567 M

Step 4: The initial concentration of H2S is 0.1567 M

The initial concentration of H2 and S2 is 0M

There will react 2X of H2S, that means there will be also produced 2X of H2 and X of S2 ( Since the ratio is 2:2:1).

The final concentration of H2S is 0.1567 - 2X

The final concentration of H2 is 2X

The final concentration of S2 is X

Step 5: Write the Kc

Kc =9.3 * 10^-8 =  ([S2]*[H2]² )/ [H2S]²

Kc = 9.3 * 10^-8 = X *(2X)² / (0.1567 - 2X)²

4X³ = 0.1567²X * 9.3*10^-8

if we calculate X = 0.000829571

The concentration of S2 at equilibrium = X = 0.000829571 M

The  concentration of H2 at equilibrium = 2X = 0.001659 M

did you find the answer?

lithosphere and asthenosphere