Question

Question #91ed4

Answer 1

Here's what I got.

Explanation:

Assuming that you're supposed to calculate the solution's percent concentration by mass, `"% m/m"`, your starting point here will be to use the density of the solution to calculate its mass.

The solution is said to have a density of `"1.12 g mL"^(-1)`, which means that every milliliter of this solution has a mass of `"1.12 g"`.

Your sample will thus have a mass of

`5.00 * 10^2color(red)(cancel(color(black)("mL"))) * "1.12 g"/(1color(red)(cancel(color(black)("mL")))) = "560 g"`

Now, the solution's percent concentration by mass tells you how much solute, which in your case is sodium chloride, `"NaCl"`, you get for every `"100 g"` of solution.

Since you know that `"560 g"` of solution contain `"21.0 g"` of sodium chloride, you can say that `"100 g"` of solution will contain

`100 color(red)(cancel(color(black)("g solution"))) * "21.0 g NaCl"/(560color(red)(cancel(color(black)("g solution")))) = "3.75 g NaCl"`

This means that the solution has a percent concentration by mass equal to

`color(green)(bar(ul(|color(white)(a/a)color(black)("% m/m " = " 3.75% NaCl")color(white)(a/a)|)))`

The answer is rounded to three sig figs.

SIDE NOTE At room temperature, a sodium chloride solution of density equal to `"1.12 g mL"^(-1)` has a percent concentration by mass of about `11%`, so make sure to let me know if this is not the correct interpretation of the problem.

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