# Calculate the percent by mass of NaCl in a solution made by dissolving 8.00 g of NaCl in 40.0 g...

## Question:

Calculate the percent by mass of NaCl in a solution made by dissolving 8.00 g of NaCl in 40.0 g of water.

a. 0.2% (w/w) NaCl

b. 20% (w/w) NaCl

c. 5% (w/w) NaCl

d. 0.05% (w/w) NaCl

## Solution Concentration Expression:

The concentration of a solution can be expressed in many ways depending on what is convenient for the method that the solution will be used for. Below are examples on how to expressed solution concentrations:

1. percent by mass: the mass of the solute is divided by the mass of the solution multiplied by 100

2. percent by volume: the volume of the solute is divided by the volume of the solution multiplied by 100

3. molarity: the mole of the solute is divided by the liters of solution

4. molality: the mole of the solute is divided by the kilogram of solvent.

For the first two expressions, the unit of the numerator should be similar to the unit of the denominator.

$$\text{%}(\frac{w}{w}) = \frac{mass~solute}{mass~solution} \times 100\text{%}$$