Question

What is the concentration in m/m% of a solution prepared from 50.0 g NaCl and 150.0 g of water?

Answer 1

`25.0%`

Explanation:

A solution's mass by mass percent concentration, `"m/m%"`, tells you the number of grams of solute present for every `"100 g"` of solution.

Your solution contains two substances: sodium chloride, `"NaCl"`, the solute, and water, the solvent. To find the total mass of the solution, add the mass of the solute and the mass of the solvent.

`"mass solution = 50.0 g + 150.0 g"`

`"mass solution = 200.0 g"`

Now, this solution contains `"50.0 g"` of solute in

`"200.0 g" = color(red)(2) * "100.0 g"`

of solution. This means that `"100.0 g"` of solution will contain

`"50.0 g"/color(red)(2) = "25.0 g"`

of solute. Since this represents the amount of solute present in `"100.0 g"` of solution, you can say that the mass by mass percent concentration is equal to

`color(darkgreen)(ul(color(black)("m/m% = 25.0% NaCl")))`

The answer is rounded to three sig figs.