pH increases while pOH decreases with rise in temperature
B
pH decreases while pOH increases with rise in temperature
C
both pH and pOH decreases with rise in temperature
D
both pH and pOH increases with rise in temperature
Text Solution
AI Generated Solution
The correct Answer is:
**Step-by-Step Solution:**
1. **Understanding the Dissociation of Water:**
Pure water undergoes a self-ionization process where it dissociates into hydrogen ions (H⁺) and hydroxide ions (OH⁻):
\[
H_2O \rightleftharpoons H^+ + OH^-
\]
2. **Recognizing the Nature of the Reaction:**
This dissociation is an endothermic reaction, meaning it absorbs heat. In endothermic reactions, an increase in temperature favors the formation of products.
3. **Applying Le Chatelier's Principle:**
According to Le Chatelier's principle, if the temperature of the system is increased, the equilibrium will shift to the right to absorb the added heat. This means that the concentrations of H⁺ and OH⁻ ions will increase.
4. **Effect on pH and pOH:**
- The pH is defined as:
\[
pH = -\log[H^+]
\]
- The pOH is defined as:
\[
pOH = -\log[OH^-]
\]
Since both [H⁺] and [OH⁻] increase with temperature, the values of pH and pOH will decrease.
5. **Conclusion:**
Therefore, with an increase in temperature, both pH and pOH of pure water decrease.
**Final Answer:**
With an increase in temperature, both pH and pOH decrease for pure water.
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