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Enter your answer in the provided box. Hydrogen sulfide decomposes according to

ID: 979648 • Letter: E

Question

Enter your answer in the provided box.

Hydrogen sulfide decomposes according to the following reaction, for which

Kc = 9.30 × 108 at 700°C:

2 H2S(g) 2 H2(g) + S2(g)

If 0.55 mol of H2S is placed in a 3.0L container, what is the equilibrium concentration of H2(g) at 700°C?

? M Enter your answer in the provided box.

Hydrogen sulfide decomposes according to the following reaction, for which

Kc = 9.30 × 108 at 700°C:

2 H2S(g) 2 H2(g) + S2(g)

If 0.55 mol of H2S is placed in a 3.0L container, what is the equilibrium concentration of H2(g) at 700°C?

? M

Explanation / Answer

The equilibrium concentration of H is 0.012 mol/L.

Calculate the initial concentrations

[HS] = 0.29mol3.0L = 0.096 67 mol/L (2 significant figures + 2 guard digits)

Write the balanced equation and set up an ICE table.

2HS 2H + S
I/mol·L¹: 0.096 67; 0; 0
C/mol·L¹: -2x; +2x; +x
E/mol·L¹: 0.096 67 - 2x; 2x; x

Write the Kc expression and solve for x

Kc=[H]2[S][HS]2 = 9.30 × 10

(2x)2×x(0.09667–2x)2 = 9.30 × 10

Because Kc is so small, we can assume that 2x is negligible compared to 0.09667. Then we have

4x30.096672 = 9.30 × 10

4x3 = 0.096 67² × 9.30 × 10 = 8.691 × 10¹

x3 = 2.173 × 10¹

x = 6.012 × 10

1

[H] = 2x mol/L= 2 × 6.012 × 10 mol/L = 0.001 20 mol/L