# Question 11d9c

Mar 29, 2016

$\text{0.99 M}$

#### Explanation:

The problem doesn't provide you with the number of moles of sodium chloride, $\text{NaCl}$, because it wants you to convert the given mass to moles by using the compound's molar mass.

A compound's molar mass tells you the mass of one mole of that compound. This means that if you know the molar mass, you can use it a conversion factor to go from moles to grams or vice versa.

In this case, sodium chloride has a molar mass of ${\text{58.44 g mol}}^{- 1}$. This means that one mole of sodium chloride has a mass of $\text{58.44 g}$.

Use this value to convert the mass of the sample to moles

58color(red)(cancel(color(black)("g"))) * overbrace("1 mole NaCl"/(58.44color(red)(cancel(color(black)("g")))))^(color(purple)("molar mass of NaCl")) = "0.9925 moles NaCl"

Now, to find the molarity of the solution, simply divide the number of moles by the volume of the solution.

$\textcolor{b l u e}{| \overline{\underline{\textcolor{w h i t e}{\frac{a}{a}} c = {n}_{\text{solute"/V_"solution}} \textcolor{w h i t e}{\frac{a}{a}} |}}}$

In your case, you will have

c = "0.9925 moles"/"1.0 L" = color(green)(|bar(ul(color(white)(a/a)"0.99 M"color(white)(a/a)|)))#

The answer is rounded to two sig figs.