Question

Kb = 1.8 x 10-5 for NH3. Will addition of each of the following to separate 100. mL samples of 0.10 M NH3 at a constant temperature of 25°C cause the pH of the resultant solution to be lower than, higher than, equal to, or cannot be determined compared with the pH of the original 100. mL sample? For each, completely justify your choice.

A)Some solid ammonium nitrate

B)Some water

C)Some 0.20 M NaOH

Answer 1

A ) on solid ammonium nitrate the pH will be decreasesd . becuause it can form buffer . NH3 is only pure base when we add NH4NO3 it is the salt of weak base and strong acid . so some acid character is dominent so pH will be decreases ( less than)

B) pH will be decreased. ( less than)

on addition of pure water volume of increases as a result NH3 molarity decreased if NH3 molarity decreased the pH also decreased.

C) NaOH

addtion of NaOH will cause to increase in pH it is due to both are bases . here NaOH is stronger base than NH3 . so pH will be very high ( more than)