Find the pH of the following solutions

a) 50 ml of 0.1 M HCl + 50 ml of 0.01 M HCl
b) 50 ml of 0.1 M HCl + 50 ml of 0.1 M H2SO4
c) 50 ml of 0.1 M HCl + 50 ml of 0.1 M CH3COOH (Ka=1.8x10-5)
d) 50 ml of 0.1 M HCl + 20 ml of 0.1 M NaOH
e) 50 ml of 0.1 M HCl + 50 ml of 0.1 M NaOH
f) 20 ml of 0.1 M HCl + 50 ml of 0.1 M NaOH
g) 50 ml of 0.1 M HCN(Ka=10-5) + 50 ml 0.1 M CH3COOH(Ka=1.8x10-5)

3 Answers

1357
Manish Shankar ·

h) 50 ml of 0.1 M HCl + 25 ml of 0.1 M NH3(Kb=1.8x10-5)

30
Ashish Kothari ·

1) Millimoles of 0.1M HCl = 5

Millimoles of 0.01M HCl=0.5

Total millimoles=5.5

[H+]= 5.5/100

pH= 2 - 0.74 = 1.26

2) Millimoles of HCl=5

Millimoles of H2SO4 = 10

Total millimoles of H+=15

Concentration = 15/100 =

pH= 2 - 1.176= 0.824

3) Millimoles of HCl = 5

[H+]= 5/100

pH=2-0.7=1.3

4) After neutralisation,

Millimoles of HCl left = 3

[H+] = 3/70

pH= 1.84

5) Clearly, pH = 7

30
Ashish Kothari ·

6) After neutralisation,

Millimoles of NaOH left = 3

[OH-]=3/70

pOH=1.84

pH = 14-1.84 = 12.16

7) Millimoles of HCN, CH3COOH = 5

[H+]=√(Ka1C1+Ka2C2)
=√(1.8x10-5x5/100 + 10-5x5/100)

pH= 4-1.072 = 2.928

8) After neutralisation,

Millimoles of HCl left = 2.5

[H+]= 2.5/75=1/30

pH = 1.477

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