Answer
$$K_c = 1.10 \times 10^7$$
Work Step by Step
1. Write the equilibrium constant expression:
- The exponent of each concentration is equal to its balance coefficient.
$$K_c = \frac{[Products]}{[Reactants]} = \frac{[ H_2S ]^{ 2 }}{[ H_2 ]^{ 2 }[ S_2 ]}$$
2. Find each concentration:
$[H_2] = 2.50/12 = 0.208 M$
$[S_2] = (1.35 \times 10^{-5})/12 = 1.13 \times 10^{-6}M$
$[H_2S] = 8.70/12 = 0.725 M$
3. Substitute the values and calculate the constant value:
$$K_c = \frac{( 0.725 )^{ 2 }}{( 0.208 )^{ 2 }( 1.13 \times 10^{-6} )} = 1.10 \times 10^{7}$$
