Question

A student needs 2.1 liters of a 0.23 molar solution for an experiment. How many grams of solute does the student need if the molar mass of the solute is 12.39 g/mol? Round your answer to the nearest 0.01, and remember to include units (properly abbreviated), BUT NOT THE SUBSTANCE

Answer 1

Molarity has the following equation:

$M=\frac{\text{solute moles}}{Liters\text{ of solution}}$

In this case, we need to find the solute mass given that the liters of solution are 2.1L and the molarity of the solution is 0.23 molar. Replacing:

$0.23M=\frac{\text{solute moles}}{2.1L}\to solute\text{ }moles=0.23M+2.1L=0.483\text{ moles}$

We have 0.483 moles of solute. To find the mass, we multiply by the molar mass:

$0.483\text{moles}\cdot\frac{12.39g}{1\text{mol}}=5.98$

Therefore, there are 5.98g of solute.