| 1. | –13.73 cal | 2. | 1372.60 cal | 
| 3. | –137.26 cal | 4. | –1381.80 cal | 
| 1. | Weak acid and it's salt with a strong base. | 
| 2. | Equal volumes of equimolar solutions of weak acid and weak base. | 
| 3. | Strong acid and its salt with a strong base. | 
| 4. | Strong acid and its salt with a weak base. (The pKa of acid = pKb of the base) | 
| 1. | \(1 \times 10^{-4}\) | 
| 2. | \(1 \times 10^{-6} \) | 
| 3. | \(1 \times 10^{-5} \) | 
| 4. | \(1 \times 10^{-3} \) | 
| 1. | where the forward and reverse reactions have stopped. | 
| 2. | whose rate law is of zero order. | 
| 3. | where individual molecules are still reacting, but there is no net change in the system. | 
| 4. | in which all components are in the same phase. |