Question

Determine the pH of each of the following solutions.

Part A

0.17 M NH4Cl

Express your answer to two decimal places.

Part B

0.20 M NaC2H3O2

Express your answer to two decimal places.

Part C

0.20 M NaCl

Express your answer to two decimal places.

Answer 1

For all questions:

Na+ is not relevant for pH (it is not a base or an acid)

Cl- is an ineffective base (not relevant for pH), because it is the conjugate base of a strong acid..

A. NH₄⁺ is a weak acid, pKa = 9.25

                 pH= 0.5pKa -0.5logC_acid = 4.625 +0.385= 5.01

B. CH₃COO^- is a weak base, pKb = 9.25

                pOH= 0.5pKb -0.5logC_base = 4.625 +0.35= 4.97

                 pH -pOH = 9.03

C. Only the water dissociation is relevant here.   pH= 7.00