## Chemistry 10th Edition

$K_c = 0.10$
1. Write the equilibrium constant expression: - The exponent of each concentration is equal to its balance coefficient. $K_c = \frac{[Products]}{[Reactants]} = \frac{[ PCl_5 ]}{[ PCl_3 ][ Cl_2 ]}$ 2. Substitute the values and calculate the constant value: $K_c = \frac{( 12.0 )}{( 10.0 )( 9.0 )} = 0.13$