You measured the pH of a 0.01M NaOH solution (strong base) and it was 13.0. The, you diluted this solution and measured its pH. What would you expect? The pH of the diluted solution would be higher because [OH-] is higher The pH of the diluted solution would be higher because [OH-] is lower O The pH of the diluted solution would be lower because [OH] is lower The pH of the diluted solution would be lower because [OH-] is higher

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Chapter1: Chemical Foundations
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**Understanding pH Changes upon Dilution**

In this exercise, we examine the effects of dilution on the pH of a NaOH solution. Here's the scenario:

- You measured the pH of a 0.01M NaOH solution (a strong base), and it read 13.0.
- Next, you diluted this solution and measured its pH again. 

**Question: What would you expect?**

**Options:**

1. The pH of the diluted solution would be higher because [OH⁻] is higher.
2. The pH of the diluted solution would be higher because [OH⁻] is lower.
3. The pH of the diluted solution would be lower because [OH⁻] is lower.
4. The pH of the diluted solution would be lower because [OH⁻] is higher.

To answer this question, consider the relationship between [OH⁻] (hydroxide ion concentration) and pH in the context of dilution.

**Explanation:**

- NaOH (sodium hydroxide) is a strong base that dissociates completely in water.
- The pH scale ranges from 0 to 14, where lower values are more acidic, and higher values are more basic.
- For strong bases like NaOH, pH is related to the hydroxide ion concentration by the formula:
  \[\text{pOH} = -\log[\text{OH}^-]\]
  \[\text{pH} = 14 - \text{pOH}\]
- When you dilute a NaOH solution, you are effectively reducing the concentration of OH⁻ ions.

Given this understanding:
- Since dilution decreases the concentration of OH⁻ ions, this will cause an increase in pOH.
- Consequently, since pH = 14 - pOH, the pH will decrease when the pOH increases.

Thus, the correct option is:
**The pH of the diluted solution would be lower because [OH⁻] is lower.**

Understanding these principles is critical for mastering concepts related to acid-base chemistry and solution concentration effects.
Transcribed Image Text:**Understanding pH Changes upon Dilution** In this exercise, we examine the effects of dilution on the pH of a NaOH solution. Here's the scenario: - You measured the pH of a 0.01M NaOH solution (a strong base), and it read 13.0. - Next, you diluted this solution and measured its pH again. **Question: What would you expect?** **Options:** 1. The pH of the diluted solution would be higher because [OH⁻] is higher. 2. The pH of the diluted solution would be higher because [OH⁻] is lower. 3. The pH of the diluted solution would be lower because [OH⁻] is lower. 4. The pH of the diluted solution would be lower because [OH⁻] is higher. To answer this question, consider the relationship between [OH⁻] (hydroxide ion concentration) and pH in the context of dilution. **Explanation:** - NaOH (sodium hydroxide) is a strong base that dissociates completely in water. - The pH scale ranges from 0 to 14, where lower values are more acidic, and higher values are more basic. - For strong bases like NaOH, pH is related to the hydroxide ion concentration by the formula: \[\text{pOH} = -\log[\text{OH}^-]\] \[\text{pH} = 14 - \text{pOH}\] - When you dilute a NaOH solution, you are effectively reducing the concentration of OH⁻ ions. Given this understanding: - Since dilution decreases the concentration of OH⁻ ions, this will cause an increase in pOH. - Consequently, since pH = 14 - pOH, the pH will decrease when the pOH increases. Thus, the correct option is: **The pH of the diluted solution would be lower because [OH⁻] is lower.** Understanding these principles is critical for mastering concepts related to acid-base chemistry and solution concentration effects.
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