Question #10e83

1 Answer
Stefan V.
Oct 12, 2016

#"25 g"#

Explanation:

A #"10.0% w/v"# solution contains #"10.0 g"# of solute, which in your case is sodium chloride, for every #"100 mL"# of solution.

In other words, if you take a #"100 mL"# sample of this solution you will end up with #"10.0 g"# of sodium chloride, dissolved in solution, of course.

You are told that the volume of the solution is equal to #"250 mL"#. Since you know that you get #"10.0 g"# of sodium chloride per #"100 mL"# of solution, you can say that the given sample must contain

#250 color(red)(cancel(color(black)("mL solution"))) * overbrace("10.0 g NaCl"/(100color(red)(cancel(color(black)("mL solution")))))^(color(blue)(="10.0% w/v")) = color(green)(bar(ul(|color(white)(a/a)color(black)("25 g NaCl")color(white)(a/a)|)))#

The answer is rounded to two sig figs.

So, in order to make your solution, you should dissolve #"25 g"# of sodium chloride in #"100 mL"# of water, then add enough water to get the final volume to #"250 mL"#.

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