# In the laboratory you dilute 3.24 mL of a concentrated 3.00 M hydrobromic acid solution to a...

## Question:

In the laboratory you dilute 3.24 mL of a concentrated 3.00 M hydrobromic acid solution to a total volume of 100 mL. What is the concentration of the dilute solution?

## Measuring the Concentration Of Solutions:

A solution contains a solute (e.g., a salt) dissolved in a precise quantity of solvent (e.g., water). To be able to achieve a quantitative understanding of its reactions with other compounds, it is important to know its concentration. One useful measure is the molarity, defined as the number of moles of solute present in one litre of aqueous solution.

The concentration of our solution is given as 3.00 M, i.e., 3.00 mol/L. Of this solution, we take out a sample of volume 3.24 mL (i.e., 0.00324 L). How many moles of HBr are in it? We can answer this by evaluating:

{eq}0.00324 \ L \times 3 \ mol/L = 0.00972 \ mol {/eq}.

This is the same number of moles that is now present in the diluted sample of volume 100 mL (i.e., 0.1 L). The concentration of the dilute solution is thus:

{eq}\displaystyle \frac{0.00972 \ mol}{0.1 \ L} = 0.0972 \ M. {/eq}