Question

In a titration of 47.35 mL of 0.3788 M ammonia with 0.3788 M aqueous nitric acid, what is the pH of the solution when 47.35 mL of the acid have been added?

Answer 1

Ammonia is a weak base , Nitric acid is a strong acid . Thus , at equivalence point , salt hydrolysis of Ammonium Nitrate will occur .

However , at the same concentration of both acid and base and the same strength , condition surely indicates the situation to be at equivalence .

Thus , pH should be guided by salt hydrolysis .

pk_b(NH₃)=4.75

Concentration of salt -

0.3788 x 47.35 INH4NO3] = M 47.35 + 47.35 = 0.1894 M

pH = 7 – 0.5 x pko - 0.5 x log NH4NO3

:.pH = 7 – 0.5 x 4.75 -0.5 x log0.1894

pH = 7 – 2.375 + 0.361

..pH = 4.98

[ANSWER]