Calculate the concentration of a NaOH solution that has a pH of 11.3.

• A. 2.0 x 10^-3 M
• B. 1.0 x 10^-2 M
• C. 5.0 x 10^-3 M
• D. 7.9 x 10^-3 M

Answer: (C)

Verified step by step guidance

1. Understand that pH is a measure of the hydrogen ion concentration in a solution. The pH scale is logarithmic, and a pH of 7 is neutral. A pH greater than 7 indicates a basic solution.
2. Recall the relationship between pH and pOH: \( \text{pH} + \text{pOH} = 14 \). Since the pH is given as 11.3, calculate the pOH by subtracting the pH from 14.
3. Use the formula \( \text{pOH} = -\log[\text{OH}^-] \) to find the hydroxide ion concentration. Rearrange this formula to solve for \([\text{OH}^-]\): \([\text{OH}^-] = 10^{-\text{pOH}}\).
4. Substitute the calculated pOH value into the equation \([\text{OH}^-] = 10^{-\text{pOH}}\) to find the concentration of hydroxide ions in the solution.
5. The concentration of NaOH in the solution is equal to the concentration of \([\text{OH}^-]\) because NaOH dissociates completely in water. Therefore, the concentration of NaOH is the same as the \([\text{OH}^-]\) concentration calculated in the previous step.