5. A solution with a \( \mathrm{pH}=11 \) is

To determine the nature of a solution with a \( \mathrm{pH} = 11 \), we can follow these steps: 1. **Understanding pH Scale**: The pH scale ranges from 0 to 14, where: - A pH of 7 is considered neutral (pure water). - A pH less than 7 indicates an acidic solution. - A pH greater than 7 indicates a basic (alkaline) solution. 2. **Analyzing the Given pH**: Since the given pH is 11, which is greater than 7, we can conclude that the solution is basic. 3. **Calculating the Concentration of Hydroxide Ions**: The relationship between pH and the concentration of hydroxide ions (\( \mathrm{OH^-} \)) can be expressed using the formula: \[ \mathrm{pOH} = 14 - \mathrm{pH} \] Therefore, we can calculate the pOH: \[ \mathrm{pOH} = 14 - 11 = 3 \] 4. **Finding the Concentration of Hydroxide Ions**: The concentration of hydroxide ions can be calculated using the formula: \[ [\mathrm{OH^-}] = 10^{-\mathrm{pOH}} \] Substituting the value of pOH: \[ [\mathrm{OH^-}] = 10^{-3} \] 5. **Conclusion**: The solution with a \( \mathrm{pH} = 11 \) is basic, and the concentration of hydroxide ions is \( 10^{-3} \, \mathrm{mol/L} \). Thus, the final answer is that a solution with a \( \mathrm{pH} = 11 \) is basic.