Question

A 0.69-g sample of lime (CaO) is dissolved in enough water to make 1535 mL of solution. Calculate the pH of of the solution.

Answer 1

Answer:

pH = 12.2

Explanation:

Given data:

Mass of lime = 0.69 g

Volume = 1535 mL (1535 / 1000 = 1.535 L)

pH of solution = ?

Solution:

First of all we will determine the molarity.

Molarity = moles of solute / volume in litter

Number of moles = mass / molar mass

Number of moles = 0.69 g / 56.1 g/mol

Number of moles = 0.0123 mol

Molarity = moles of solute / volume in litter

Molarity = 0.0123 mol / 1.535 L

Molarity =  0.008 M

One mole of CaO neutralize two mole of OH⁻.

0.008 M×2 = 0.016 M

[OH⁻] = 0.016 M

pOH = -log [OH⁻]

pOH = [0.016]

pOH = 1.8

14 = pH +pOH

pH = 14 - pOH

pH = 14-1.8

pH = 12.2