Question

50 ml of 0.05 M HNO₃ is added to 50 ml of 0.025 M KOH. Calculate the pH of the resultant solution.

Answer 1

Number of moles of HNO₃ = 0.05 x 50 x = 2.5 x 10^-3 

Number of moles of KOH = 0.025 x 50 x 10^-3 = 1.25 x 10^-3

Number of moles of HNO₃ after mixing = 2.5 x 10^-3 – 1.5 x 10^-3

= 1.25 x 10^-3

After mixing, total volume = 100 ml = 100 x 10^-3 L

pH = – log [H⁺]

pH = – log (1.25 x 10^-2) = 2 – 0.0969 

= 1.9031