Question

Muriatic acid (hydrochloric acid, HCl) is routinely used to clean swimming pools.

a) If a muriatic acid solution has a pH of 3.00, what is the hydronium ion concentration (hydronium ion concentration is also the muriatic acid concentration)?

b) What is the hydroxide ion concentration for muriatic acid?

c) If 1.00L of the this muriatic acid is poured to 5.00L water, what is the new molar concentration and the pH of the muriatic solution?   Hint: use C1•V1 = C2•V2

Answer 1

A)

pH = 3.00

[H+] = 10^-pH

         = 10^-3.00

         = 1.0 x 10^-3 M

hydronium ion concentration = 1.0 x 10^-3 M

b)

[H3O+] [OH-] = 1.0 x 10^-14

1.0 x 10^-3 [OH-] = 1.0 x 10^-14

[OH-] = 1.0 x 10^-11 M

hydroxide ion concentration = 1.0 x 10^-11 M

c)

C1 V1 = C2 V2

1.0 x 10^-3 x 1 = C2 x (1 + 5)

C2 = 1.67 x 10^-4 M

new molar concentration = 1.67 x 10^-4 M

pH = -log [H+]

pH   = -log (1.67 x 10^-4)

pH = 3.78