Question

What mass of NaCl is needed to make 2.50 L of a 2.20 M of a NaCl Solution?

Answer 1

`"321 g"`

Explanation:

All you need to know here is that the molarity of a solution tells you the number of moles of solute present in exactly `"1 L"` of the solution.

In your case, a `"2.20-M"` sodium chloride solution will contain `2.20` moles of sodium chloride, the solute, for every `"1 L"` of the solution.

So if every `"1 L"` of this solution must contain `2.20` moles of sodium chloride in order for the solution to have a molarity of `"2.20 M"`, it means that `"2.50 L"` of this solution must contain

`2.50 color(red)(cancel(color(black)("L solution"))) * "2.20 moles NaCl"/(1color(red)(cancel(color(black)("L solution")))) = "5.50 moles NaCl"`

To convert the number of moles of sodium chloride to grams, use the molar mass of the compound.

`5.50 color(red)(cancel(color(black)("moles NaCl"))) * "58.4 g"/(1color(red)(cancel(color(black)("mole NaCl")))) = color(darkgreen)(ul(color(black)("321 g")))`

The answer is rounded to three sig figs.