Question

Calculate the [H3O+] and [OH−] for a solution with the following pH values: pH=10.6 Express your answers using one significant figure separated by a comma. pH=4.9 Express your answers using one significant figure separated by a comma. pH=7.10 pH=6.7 pH=1.72

Answer 1

pH = 10.6

[H3O+] = 10^-pH = 10^-10.6 = 2.51188*10^-11

1 sig fig. ---> 2*10^-11

[OH-] = Kw/[H3O+] = (10^-14)/(2.51188*10^-11) = 0.00039810818

1 sig fi. ---> 4*10^-4

2)

pH = 4.9

[H3O+] = 10^-pH = 10^-4.9 = 0.000012589 = 1.25*10^-5

1 sig fig --> 1*10^-5

[OH-] = Kw/[H3O+] = (10^-14)/(0.000012589 ) = 7.9434*10^-10

1 sig fig --> 8*10^-10

3)

pH = 7.1

[H3O+] = 10^-pH = 10^- 7.1 = 7.9432*10^-8

1 sig fig --> 8*10^-8

[OH-] = Kw/[H3O+] = (10^-14)/( 7.9432*10^-8 ) = 1.2589*10^-7

1 sig fig --> 8*10^-7

4)

pH = 6.7

[H3O+] = 10^-pH = 10^- 6.7 = 1.9952*10^-7

1 sig fig --> 2*10^-7

[OH-] = Kw/[H3O+] = (10^-14)/(1.9952*10^-7 ) = 5.0120*10^-8

1 sig fig --> 5*10^-8

5)

pH = 1.72

[H3O+] = 10^-pH = 10^- 1.72 =0.01905

1 sig fig --> 2*10^-2

[OH-] = Kw/[H3O+] = (10^-14)/(0.01905 ) = 5.249*10^-13

1 sig fig --> 5*10^-13