Write equations and the expressions for Ke for these reversible reactions: (a) the reaction of hydrogen with chlorine to make hydrogen chloride.

At $T_1 = 700 \text{ K}$, $K_c = 5.1$.
At $T_2 = 1100 \text{ K}$ (assuming $1100 \text{ °C}$ in the question refers to $1100 \text{ K}$ for consistency with the first temperature unit, or $1373 \text{ K}$ if it's $1100 \text{ °C}$. The conclusion remains the same as temperature increases in both cases), $K_c = 1.0$.

As the temperature increases from $700 \text{ K}$ to $1100 \text{ K}$, the value of $K_c$ decreases from 5.1 to 1.0.

For an exothermic reaction, increasing the temperature shifts the equilibrium to the left (towards reactants) to absorb the added heat. This results in a decrease in the concentration of products and an increase in the concentration of reactants, thus decreasing the value of $K_c$.
For an endothermic reaction, increasing the temperature shifts the equilibrium to the right (towards products) to absorb the added heat. This results in an increase in the concentration of products and a decrease in the concentration of reactants, thus increasing the value of $K_c$.

Since an increase in temperature leads to a decrease in $K_c$, the reaction is exothermic.

The reaction is exothermic.
Reason: As the temperature increases from $700 \text{ K}$ to $1100 \text{ K}$, the equilibrium constant $K_c$ decreases from 5.1 to 1.0. This indicates that increasing the temperature shifts the equilibrium to the left (towards reactants), which is characteristic of an exothermic reaction according to Le Chatelier's principle.