Question #10e83

1 Answer
Stefan V.
Oct 12, 2016

"25 g"25 g

Explanation:

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

In other words, if you take a "100 mL"100 mL sample of this solution you will end up with "10.0 g"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"250 mL. Since you know that you get "10.0 g"10.0 g of sodium chloride per "100 mL"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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