# Question #608c2

##### 1 Answer

#### Explanation:

As you know, a solution's **percent concentration by mass** tells you the number of grams of solute present for every

In your case, the solution is said to be

Consequently, this

#"mass of solvent" = overbrace("100 g")^(color(blue)("mass of solution")) - overbrace("3.22 g")^(color(blue)("mass of solute"))#

#"mass of solvent = 96.78 g"#

of water, the solvent. Now, in order to find the **molality** of the solution, you need to figure out how many *moles* of sodium nitrate are present for every

Since you know how many grams of sodium nitrate are present for every

#10^3 color(red)(cancel(color(black)("g water"))) * "3.22 g NaNO"_3/(96.78color(red)(cancel(color(black)("g water")))) = "33.27 g"#

then use the **molar mass** of sodium nitrate to convert the number of grams to *moles*.

#33.27 color(red)(cancel(color(black)("g"))) * "1 mole NaNO"_3/(84.9947color(red)(cancel(color(black)("g")))) = "0.391 moles NaNO"_3#

You can thus say that the **molality** of the solution, i.e. the number of moles of sodium nitrate present for every

#color(darkgreen)(ul(color(black)("molality = 0.391 mol kg"^(-1))))#

The answer is rounded to three **sig figs**, the number of sig figs you have for the percent concentration of the solution.