Question

What would be the resulting molarity of a solution made by dissolving 45.7 grams of Mg(OH)2 in enough water to make a 1087-milliliter solution? Show all of the work needed to solve this problem

Answer 1

Answer: The molarity of the solution is 0.72 M

Explanation:

Molarity is defined as the number of moles present in one liter of solution.

Mathematically,

$\text{Molarity of the solution}=\frac{\text{Mass of solute}\times 1000}{\text{Molar mass of solute}\times \text{Volume of solution (in mL)}}$

We are given:

Mass of magnesium hydroxide = 45.7 g

Molar mass of magnesium hydroxide = 58.32 g/mole

Volume of solution = 1087 mL

Putting values in above equation, we get:

$\text{Molarity of the solution}=\frac{45.7\times 1000}{58.32\times 1087}=0.72M$

Hence, the molarity of the solution is 0.72 M

Answer 2

Molar mass Mg(OH)2 = 58.3197 g/mol

Number of moles:

45.7 / 58.3197 => 0.7836 moles

Volume = 1087 / 1000 => 1.087 L

Therefore:

Molarity = moles / volume

Molarity = 0.7836 / 1.087

=> 0.7208 M