Question

Could someone show me how to do this correctly please. Thanks.
III) What is the pH of a 0.025 M aqueous solution of HClO4 at 25°C?
IV) What is the pH of a 0.025 M aqueous solution of Ba(OH)2 at 25°C?
V) What is the concentration (in M) of hydrogen ions in a solution at 25°C with pH=12.4?
VI) Calculate the pOH of a solution containing 2.37×10^-5 M H3O+ at 25°C

Answer 1

iii)  a 0.025 M aqueous solution of HClO4 has

[H3O+] = 0.025 M

therefore

pH = - log[H3O+]

= - log 0.025

= 1.60

1V) a 0.025 M aqueous solution of Ba(OH)2 has

[OH-] = 2 x 0.025 M = 0.050 M

therefore

pOH = -log[OH-]

= - log 0.050

= 1.30

and pH + pOH = 14 therefore

pH = 14 - 1.30

= 12.70

V) for pH = 12.4

therefore

[H3O+] = 10^-12.4

= 3.98 x 10^-13 M

VI) for [H3O+] = 2.37 x 10^-5 M , we have

pH = - log[H3O+]

= 4.63

And pH + pOH = 14 therefore

pOH = 14 - pH

= 14 - 4.63

= 9.37