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?

1 Answer
Sep 16, 2017

Answer:

#"18% m/m"#

Explanation:

The first thing that you need to do here is to use the density of the solution to determine the mass of #"150 mL"# of this hydrochloric acid solution.

The density of the solution is said to be equal to #"1.1 g mL"^(-1)#, so right from the start, you know that every #"1 mL"# of solution will have a mass of #"1.1 g"#.

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, #"% m/m"#, you need to figure out the mass of hydrochloric acid present in #"100 g"# of this solution.

Since you know that #"165 g"# of solution contain #"30. g"# of hydrochloric acid, you can say that #"100 g"# of this solution will contain

#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.