If molarity moles/liter, then how many grams of NaCl are needed to make 3.550 liter of a 1.30 M solution?

1 Answer
Nov 22, 2016

"270. g"

Explanation:

Molarity is indeed defined as moles of solute per liter of solution, but it can also be expressed as grams of solute per liter of solution.

As you know, a "1 M" solution contains exactly 1 mole of solute in "1 L" of solution.

In your case, a "1.30 M" sodium chloride solution will contain 1.30 moles of sodium chloride, the solute, for every "1 L" of solution.

You can use the molar mass of sodium chloride to convert this to grams of sodium chloride for every "1 L" of solution.

1.30 color(red)(cancel(color(black)("moles NaCl"))) * "58.44 g"/(1color(red)(cancel(color(black)("mole NaCl")))) = "75.97 g"

You can now say that a "1.30 M" sodium chloride solution must contain "75.97 g" of sodium chloride for every "1 L" of solution. Now all you have to do is use this concentration to figure out how many grams would be needed to make your sample

3.550 color(red)(cancel(color(black)("L solution"))) * "75.97 g NaCl"/(1color(red)(cancel(color(black)("L solution")))) = color(darkgreen)(ul(color(black)("270. g NaCl")))

The answer is rounded to three sig figs.