Question

Calculate the pH value of the following. The concentration in each problem is 0.25M

(a) ZnCl₂

(b) KOH

(c) HF

(d) NaF

(e) KNO₃

(f) KCNO

Determine the acidity of the following. You do not have to calculate the pH value. Briefly explain your reasoning.

(a) KH₂PO₃  - Acidic, Basic, or Neutral

(b) NaHSO₄ - Acidic, Basic, or Neutral

(c) KHCO₃ - Acidic, Basic, or Neutral

(d) NaHSO₃ - Acidic, Basic, or Neutral

Answer 1

a ) ZnCl2 , pH < 7 . i could not find Ka value for Zn+2

b) KOH = 0.25 M

pOH = -log [OH-] = -log (0.25) = 0.6

pH + pOH = 14

pH = 13.4

c) HF = 0.25 M

pH = 1/2 [pKa - logC]

pH = 1/2 [3.20 - log 0.25]

pH = 1.90

d) NaF = 0.25 M

it is the salt of weak acid + strong base

so : pH = 7 + 1/2 [pKa + log C]

pH = 7 + 1/2 [3.20 + log 0.25]

pH = 8.30

e) KNO3 it is the salt of strong acid + strong base so pH = 7

f ) pKa of HCNO = 3.46

pH = 7 + 1/2 [pKa + log C]

pH = 7 + 1/2 [3.46 + log 0.25]

  pH = 8.43

2)

(a) KH2PO3  - Acidic

(b) NaHSO4 - Acidic

(c) KHCO3 - Basic

(d) NaHSO3 - Basic