The compound in the blank is $H_2$. This reaction is products-favored, because this side has the weaker acid and base.
Work Step by Step
1. Identify the other compound that is next to the blank, on the same side: - It is $OH^-$; 2. Is it acting as an acid or as a base? - As a base, because it is receiving one proton. 3. If the other compound is a base, the blank should be an acid. 4. The conjugate pair of $OH^-$ is $H_2O$, therefore, the conjugate pair of the blank compound should be $H^-$. 5. Since the compound that is missing is an acid, $H^-$ should be its conjugate base. 6. Determine the conjugate acid of $H^-$. - If we add a proton to $H^-$, it turns to $H_2$, therefore, this is the compound in the blank. ------ 1. To determine which side the reaction favors, identify the side with the weaker compounds. Acids: $H_2$ and $H_2O$ ** You can find the constants values on table 14.2, on page 624. - $H_2$ is weaker; Bases: $H^-$ and $OH^-$ - $OH^-$ is weaker. Therefore, the products side is favored.