Question

How do you calculate the grams solute required to make the following solution: 2.5 L of 0.90% of NaCl (m/v)?

Answer 1

Here's how you can do that.

Explanation:

You know that a solution's mass by volume percent concentration, `"% m/v"`, tells you the number of grams of solute present for every `"100 mL"` of solution.

This implies that a `"0.90% m/v"` solution will contain `"0.90 g"` of sodium chloride, the solute, for every `"100 mL"` of solution.

You can thus say that

`2.5 color(red)(cancel(color(black)("L"))) * (10^3color(white)(.)"mL")/(1color(red)(cancel(color(black)("L")))) = 2.5 * 10^3` `"mL"`

of `"0.90% m/v"` sodium chloride solution must contain

`2.5 * 10^3 color(red)(cancel(color(black)("mL solution"))) * "0.90 g NaCl"/(100color(red)(cancel(color(black)("mL solution"))))= color(darkgreen)(ul(color(black)("23 g NaCl")))`

The answer is rounded to two sig figs.