Answer
$$K_P = 3.8 \times 10^{4}$$
Work Step by Step
1. The exponent of each pressure is equal to its balance coefficient.
$$K_P = \frac{P_{Products}}{P_{Reactants}} = \frac{P_{ NH_3 } ^{ 2 }}{P_{ N_2 }P_{ H_2 } ^{ 3 }}$$
2. Substitute the values and calculate the constant value:
$$K_P = \frac{( 3.1 \times 10^{-2} )^{ 2 }}{( 8.5 \times 10^{-1} )( 3.1 \times 10^{-3} )^{ 3 }} = 3.8 \times 10^{4}$$
