Question

What is the molarity of a solution that has 40. g NaOH in 1.0 L of solution?

Answer 1

Molarity is defined as the moles of a substance in a volume of solution. That is, we can represent it with the following equation:

`\text{Molarity}=\frac{\text{Moles of solute}}{L\text{ of solution}}`

We are given the liters of the 1.0L solution. We must find the moles of NaOH that represent 40. g of NaOH. We will use the molar mass of NaOH. The molar mass of NaOH will be the sum of the atomic weight of each element. It means that the molar mass of NaOH will be:

So, the moles of NaOH will be:

`\begin{gathered} \text{MolNaOH}=GivengNaOH*(1molNaOH)/(MolarMass,gNaOH) \\ \text{MolNaOH}=40.gNaOH*(1molNaOH)/(39.997gNaOH)=1.0molNaOH \end{gathered}`

We have 1 mol of NaOH in 1 liter of solution. The molarity will be:

`\begin{gathered} \text{Molarity}=\frac{\text{Moles of solute}}{L\text{ of solution}} \\ \text{Molarity}=\frac{1.0\text{molNaOH}}{1.0L\text{ of solution}}=1.0M \end{gathered}`

The molarity of the solution will be 1.0M