Question

1 L of 0.1 M HCl is added to 1 L of 0.1 M HA (weak acid) solution. To this solution, 16 g of solid NaOH is added. What is the pOH value of resultant solution? (Given molar mass of NaOH is 40 g/mol, $ \log 2 = 0.3, \log 4 = 0.6 $)

• A. 13
• B. 1
• C. 12.2
• D. 6

Hint:

For weak acid and strong base reactions, calculate the excess amount of base or acid to find the pOH or pH.

Answer 1

The Correct Option is C

The moles of NaOH added is: \[ \text{Moles of NaOH} = \frac{16}{40} = 0.4 \, \text{mol} \] Since NaOH is a strong base, it completely neutralizes the weak acid \( \text{HA} \). After neutralization, the pOH is calculated based on the concentration of the remaining OH\(^-\) ions, which gives a pOH value of 12.2.