A solution of HCl in water has a density of 1.1 g/mL. What is the mass% of HCl in the solution if 150 mL of the solution contains 30. g of HCl?
The first thing that you need to do here is to use the density of the solution to determine the mass of
The density of the solution is said to be equal to
This means that your sample will have a mass of
#150 color(red)(cancel(color(black)("mL"))) * "1.1 g"/(1color(red)(cancel(color(black)("mL")))) = "165 g"#
Now, in order to find the solution's percent concentration by mass,
Since you know that
#100 color(red)(cancel(color(black)("g solution"))) * "30. g HCl"/(165color(red)(cancel(color(black)("g solution")))) = "18.18 g HCl"#
You can thus say that the solution has a percent concentration by mass equal to
#color(darkgreen)(ul(color(black)("% m/m = 18% HCl")))#
The answer is rounded to two sig figs.