The dissociation of water into H₃O⁺ and OH⁻ ions depends on temperature. At 0 °C the [H₃O⁺] = 3.38 x 10⁻⁸ M, at 25 °C the [H₃O⁺] = 1.00 x 10⁻⁷ M, and at 50 °C the [H₃O⁺] = 2.34 x 10⁻⁷ M.Is the dissociation of water endothermic or exothermic?

Verified step by step guidance

1. Identify the relationship between temperature and the concentration of H₃O⁺ ions. As temperature increases, observe how the concentration of H₃O⁺ ions changes.
2. Recall that an endothermic process absorbs heat, resulting in an increase in the concentration of products with increasing temperature. Conversely, an exothermic process releases heat, leading to a decrease in the concentration of products with increasing temperature.
3. Compare the given concentrations of H₃O⁺ ions at different temperatures: 0 °C, 25 °C, and 50 °C. Note how the concentration changes as the temperature increases.
4. Determine whether the increase in temperature results in an increase or decrease in the concentration of H₃O⁺ ions. This will help you identify if the process is endothermic or exothermic.
5. Conclude based on the observed trend: if the concentration of H₃O⁺ ions increases with temperature, the dissociation of water is endothermic. If it decreases, the process is exothermic.

Key Concepts

Dissociation of Water

The dissociation of water refers to the process where water molecules (H₂O) split into hydronium ions (H₃O⁺) and hydroxide ions (OH⁻). This equilibrium reaction is influenced by temperature, as higher temperatures generally increase the dissociation, leading to higher concentrations of H₃O⁺ and OH⁻ ions. Understanding this process is crucial for analyzing how temperature affects the ionization of water.

Endothermic vs. Exothermic Reactions

Endothermic reactions absorb heat from their surroundings, resulting in a decrease in temperature of the environment, while exothermic reactions release heat, increasing the temperature. The classification of a reaction as endothermic or exothermic can be determined by observing the temperature changes associated with the reaction. In the context of water dissociation, if increasing temperature leads to greater dissociation, it suggests that the process is endothermic.

Temperature and Equilibrium

Temperature plays a significant role in chemical equilibria, as described by Le Chatelier's principle. When the temperature of a system at equilibrium is changed, the system will adjust to counteract that change. In the case of water dissociation, an increase in temperature shifts the equilibrium towards the products (H₃O⁺ and OH⁻), indicating that the reaction absorbs heat, further supporting the idea that the dissociation is endothermic.