Question

2) calculate the [H3O+] and pH of each H2So4 solution. At approximately what concentration does the x is small approximation break down?

a) 0.50M

b) 0.10M

c) 0.050M

Answer 1

a. 0.5M H2So4

H2SO4 is strong acid. It is completely ionisable.

H2SO4 + H2O-----------------> H3O⁺   + HSO4^-

0.5M                                        0.5M

[H3O+]   = [H2SO4]

[H3O+] = 0.5M

PH = -log[H3O+]

         = -log0.5   = 0.3010

b.

H2SO4 + H2O-----------------> H3O⁺   + HSO4^-

0.1M                                        0.1M

[H3O+]   = [H2SO4]

[H3O+] = 0.1M

PH = -log[H3O+]

         = -log0.1 = 1

PH = 1

c.

H2SO4 + H2O-----------------> H3O⁺   + HSO4^-

0.05M                                        0.05M

[H3O+]   = [H2SO4]

[H3O+] = 0.05M

PH = -log[H3O+]

         = -log0.05   = 1.3010