# Question #d42e2

##### 1 Answer

Molality: **0.05 molal**.

#### Explanation:

A solution's molality is defined as the number of moles of solute, in your case sodium chloride, divided by the mass of the solvent, in your case water, expressed in **kilograms**.

This means that, for a given volume of solution, you need to know its density in order to be able to determine how much solvent you have present.

To make the calculations easier, assume a **1-L** sample of your solution. SInce its molarity is said to be **0.05 M**, the sample will contain **0.05 moles** of sodium chloride.

Use sodium chloride's molar mass to determine how many grams would contain that many moles

Now, the density of a **1-L** solution that only contains **2.922 g** of sodium chloride will be very, very close to **1.00 g/mL**.

Let's assume that the density of the solution is **1.001 g/mL**.

This means that the sample has a mass of

The mass of water will be

This means that the solution's molality will be

For all intended purposes, and taking into account the fact that you only gave one sig fig for the molarity of the solution, the molality will be