Question

Help with #17Determine the pH and pOH of each solution of the following: 17. 5 g of sodium hydroxide is dissolved in 500 ml of water. 18. 1.52 g of hydrochloric acid is dissolved in 500 ml of water. 19. 75.8 g of aluminum hydroxide in 1500 ml 20. 16.85 g of sulfuric acid is dissolved in 5000 ml of water.

Answer 1

Answer

pOH = 0.60

pH = 13.40

Explanation

Given:

Mass of NaOH = 5 g

Volume of water = 500 mL

What to find:

The pH and pOH of the solution.

Solution:

The first step is to determine the mole of NaOh in 5 g NaOH.

1 mole NaOH = 40 g/mol

So mole of NaOH in 5 g NaOH is

$Mole=\frac{5g}{40g\text{/}mol}=0.125mol$

The next step is to determine the molarity of the solution.

$Molarity=\frac{Mole}{Volume\text{ }in\text{ }L}$

Puting mole = 0.125 mol and Volume = 500/1000 = 0.5 L

$Molarity=\frac{0.125mol}{0.5L}=0.25\text{ }M$

This implies the hydroxyl ion concentration in the solution is 0.25 M

Using pOH = -log[OH⁻], the pOH can be determine.

pOH = -log(0.25)

pOH = -(-0.6021)

pOH = 0.60

Since pH + pOH = 14, then pH = 14 - pOH

Putting pOH = 0.60

pH = 14 - 0.60

pH = 13.40

Therefore, the pH of the solution = 13.40 and pOH = 0.60