Question

Test your understanding of titrations.

Write a balanced equation for the neutralization of aqueous strontium hydroxide with aqueous hydrochloric acid.

A chemist finds a strontium hydroxide solution in lab, but the concentration of this solution is not labeled. A 25.00 mL sample of strontium hydroxide solution is placed in a flask. It takes the addition of 30.00 mL of 0.2695 M HCl to reach the equivalence point. What is the molarity of the strontium hydroxide solution?

[0.1617 M]

What is the molarity of aqueous H⁺ ions in the 0.2695 M HCl solution used in this titration? (Note-­‐ Aqueous H⁺ ions are also known as H3O⁺ ions)

[0.2695 M]

You will learn more about pH later in the semester. It is a measure of the acidity or basicity of a substance. If pH = -­‐log [H⁺] or -­‐log[H3O⁺], what is the pH of the

aqueous HCl solution?

[pH = 0.5694]

Answer 1

1)

Sr(OH)2 + 2 HCl    ------------> SrCl2 + 2 H2O

mmoles of HCl = 30.00 x 0.2695

                        = 8.085

1 mol Sr(OH)2   ----------> 2 mol HCl

    ??              -----------> 8.085 mol HCl

moles of Sr(OH)2 = 4.0425 mol

4.0425 = C x 25

C = 0.1617

Molarity of Sr(OH)2 = 0.1617 M

2)

concentration of HCl = 0.2695 M

this is strong acid.

[H+] = 0.2695 M

3)

pH = -log (0.2695)

pH = 0.5694