# A student adds 6.00 g of a solid to 30.0 ml of water. What is the concentration of this solution expressed as mass/volume percent?

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(If necessary to the calculation, assume that 1.00 mL of water has a mass of 1.00gand that the total volume remains 30.0 ml.)

(If necessary to the calculation, assume that 1.00 mL of water has a mass of 1.00gand that the total volume remains 30.0 ml.)

##### 1 Answer

#### Explanation:

We use **mass by volume percent concentration**, **for every** **of solution**.

In your case, the problem mentions that the volume of the solution is equal to the volume of water, which means that **after** you dissolve the solid, you will have

As you know, solutions are homogeneous mixtures, which means that they have the same composition throughout.

This implies that you can use the known composition of the solution to *scale up* the sample to a total volume of **conversion factor**.

#100 color(red)(cancel(color(black)("mL solution"))) * "6.00 g solute"/(30.0color(red)(cancel(color(black)("mL solution")))) = "20.0 g solute"#

So, you know that

#color(darkgreen)(ul(color(black)("% m/v" = 20.0%)))#

The answer is rounded to three **sig figs**.