Question

What is the pH of each of the following aqueous solutions? (a) 0.074 M HCl WebAssign will check your answer for the correct number of significant figures. 1.13 (b) 0.11 M KOH WebAssign will check your answer for the correct number of significant figures. (c) 0.19 M Ba(OH)2 WebAssign will check your answer for the correct number of significant figures.

Answer 1

Explanation:

To calculate the pH of an aqueous solution you need to know the concentration of the hydronium ion in moles per liter (molarity). The pH is then calculated using the expression: pH = - log [H3O+].

(a) 0.074 M HCl

The HCl is a strong acid and is 100% ionized in water. The hydronium ion concentration is 0.074 M.

pH = - log [H3O+] = -log ( 0.074)

pH = 1.13

(b) 0.11 M KOH

pOH =  - log [OH-]

pOH = - log(0.11) = 0.96

pH + pOH = 14

pH = 14 - 0.96 = 13.04

(c) 0.19 M Ba(OH)2

Ba(OH)2 --> Ba2+   + 2OH-

pOH =  - log [OH-]

pOH = - log(2*0.19) = - log (0.38) = 0.42

pH + pOH = 14

pH = 14 - 0.42 = 13.58