Question

1. Calculate the [H+]-, [HSO4-]- and [SO 42-] - ion concentrations and the pH of a 0.050 M H2SO4. Ka1 is very large and Ka2 is 0.012.

2. Write equations to show how you would make:

a) NaHSO4

b) Na2SO4

c) NaHCO3

Answer 1

H2SO4 <==> H+ + HSO4^-

HSO4^- <==> H^- + SO4^2-

[H+] = 0.05 M

[HSO4^-] = 0.05 M

pH = -log[0.05] = 1.3

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	[HSO4-]	[H+]	[SO4^2-]
initial	0.05	0	0
Change	-x	+x	+x
equilibrium	0.05-x	x	x

K2 = x*x/(0.05-x)

or, 0.012 = x^2/(0.05-x)

as x is small , 0.05-x = 0.05

x = 0.024 M

So concentration of [SO4^2-] = 0.024 M

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(a) NaOH + H2SO4 = NaHSO4 + H2O

(b) NaCl + H2SO4 = Na2SO4 + HCl

(c) NaOH + H2CO3 = NaHCO3 + H2O