Question

A small amount of sodium hydroxide is added to water. When the chemical reaction reaches equilibrium, the pH is 12. Which statement
and conclusion about sodium hydroxide is correct?(1 point)
The negative log of the concentration of OH ions is 12. Sodium hydroxide is a strong acid. –
The negative log of the concentration of OH ions is 2. Sodium hydroxide is a strong acid. –
The negative log of the concentration of OH ions is 12. Sodium hydroxide is a strong base. –
The negative log of the concentration of OH ions is 2. Sodium hydroxide is a strong base.

Answer 1

To analyze the situation:

1. A pH of 12 indicates that the solution is basic. The pH scale is from 0 to 14, where values less than 7 are acidic and values greater than 7 are basic.
2. pH is related to pOH by the equation: \( \text{pH} + \text{pOH} = 14 \).
- If pH = 12, then:
\[
\text{pOH} = 14 - 12 = 2
\]

3. The concentration of hydroxide ions, \([OH^-]\), can be found using the formula:
\[
\text{pOH} = -\log[OH^-]
\]
- If \(\text{pOH} = 2\), then:
\[
[OH^-] = 10^{-2} \text{ M} = 0.01 \text{ M}
\]

4. Sodium hydroxide (NaOH) is known to be a strong base, meaning it dissociates completely in water to produce hydroxide ions.

Now, let's evaluate the provided statements:

- **The negative log of the concentration of OH ions is 12. Sodium hydroxide is a strong acid.** (Incorrect)
- **The negative log of the concentration of OH ions is 2. Sodium hydroxide is a strong acid.** (Incorrect)
- **The negative log of the concentration of OH ions is 12. Sodium hydroxide is a strong base.** (Incorrect)
- **The negative log of the concentration of OH ions is 2. Sodium hydroxide is a strong base.** (Correct)

The correct statement is: **The negative log of the concentration of OH ions is 2. Sodium hydroxide is a strong base.**