Answer
The reaction is exothermic: b)
Work Step by Step
1. Write the equilibrium constant expression:
- The exponent of each concentration is equal to its balance coefficient.
$$K_c = \frac{[Products]}{[Reactants]} = \frac{[ AB ]^{ 2 }}{[ A_2 ][ B_2 ]}$$
2. At T1:
$$K_c = \frac{(5)^2}{(1)(2)} = 12.5$$
3. At T2:
$$K_c = \frac{(3)^2}{(2)(3)} = 1.5$$
When temperature increased, $K_c$ decreased, so the equilibrium shifted to the left: The reaction is exothermic.
