Verified answer

KOH reacts with HNO3 :

KOH + HNO3 → KNO3 + H2O

1mol KOH reacts with 1 mol HNO3

Mol HNO3 in 40cm³ of 0.02M solution = 40/1000*0.02 = 0.0008 mol HNO3

Mol KOH in 60cm³ of 0.03M solution = 60/1000*0.03 = 0.0018 mol KOH

These react and 0.0018 - 0.0008 = 0.001 mol KOH remains dissolved in 40+60 = 100 cm³ solution

Molarity of KOH in solution = 0.001/0.1 = 0.01M KOH solution

Because KOH is a strong base ,

[OH-] = 0.01M First answer

Concentration of H+ ions

[H+] [OH-] = 10^-14

[H+] = 10^-14/[OH-]

[H+] = 10^-14 / 0.01

[H+] = 1*10^-12M second answer.