# How many grams of NaCl are in 225 mL of a 0.75 M NaCl solution? (The molecular weight of NaCl is 58.44 g.)

##### 1 Answer

#### Explanation:

The first thing you need to do here is to use the molarity of the solution to determine how many **moles** of sodium chloride you have in your sample.

As you know, **molarity** tells you the number of moles of solute, which in your case is sodium chloride, present in **moles** of sodium chloride **for every**

#"0.75 M: " "0.75 moles NaCl " stackrel( color(white)(a) color(blue)("for every") color(white)(aaa) )(rarr) "1 L of solution"#

You can thus use the molarity of the solution as a conversion factor to find the number of moles of sodium chloride present in your sample

#225 color(red)(cancel(color(black)("mL"))) * (1 color(red)(cancel(color(black)("L"))))/(10^3color(red)(cancel(color(black)("mL")))) * "0.75 moles NaCl"/(1color(red)(cancel(color(black)("L solution")))) = "0.16875 moles NaCl"#

To convert this to *grams*, use the **molar mass** of sodium chloride

#0.16875 color(red)(cancel(color(black)("moles NaCl"))) * "58.44 g"/(1color(red)(cancel(color(black)("mole NaCl")))) = color(darkgreen)(ul(color(black)("9.9 g")))#

The answer is rounded to two **sig figs**, the number of sig figs you have for the molarity of the solution.