Question

Which of the following solutions would have same pH?

• A. 100 ml of 0.2 M HCl + 100 ml of 0.4 M NH3
• B. 50 ml of 0.1 M HCl + 50 ml of 0.2 M NH3
• C. 100 ml of 0.3 M HCl + 100 ml of 0.6 M NH3
• D. All will have same pH.

Answer 1

Answer: (D)

All will have same pH.

Answer 2

(1) NH4OH + HCI $\longrightarrow$NH4CI + H2O

0.2 M 0.1 0 0

0.1 0 0.1 0.1

pOH = pKb

(2) NH4OH + HCI $\longrightarrow$ NH4CI + H2O

0.1 0.05 0 0

0.05 0 0.05

pOH = pKb + log $\left( \frac{0.05}{0.05} \right)$= pKb

(3) NH4OH + HCI $\longrightarrow$ NH4CI + H2O

0.3 0.15

0.15 0 0.15

pOH = pKb So all solution have same pH