Question

A magnesium hydroxide solution is prepared by adding 10.00 g of magnesium hydroxide to a volumetric flask and bringing the final volume to 1.00 L by adding water buffered at a pH of 7.0. What is the concen- tration of magnesium in this solution? (Assume that the temperature is 25◦C and the ionic strength is negligible).

Answer 1

Answer:

0.1724 M is the concentration of magnesium ions in this solution.

Explanation:

Mass of magnesium hydroxide gas = 10.00 g

Molar mass of magnesium hydroxide = 58 g/mol

Moles of magnesium hydroxide = $\frac{10.00 g}{58 g/mol}=0.1724 mol$

Volume of the solution = V = 1.00 L

Molarity or concentration of the magnesium hydroxide:M

$M=\frac{\text{Moles of solute}}{\text{Volume of solution in L}}$

$M=\frac{0.1724 mol}{1.00 L}=0.1724 M$

1 mole of magnesium hydroxide contains 1 mole of magnesium ion.Then 0.1724 M of magnesium hydroxide will have :

$[Mg^{2+}]=1\times 0.1724 M=0.1724 M$

0.1724 M is the concentration of magnesium ions in this solution.