Question

Question #3501f

Answer 1

`"20 moles BaCl"_2`

Explanation:

Molarity is simply a measure of the number of moles of solute present in `"1 L"` of solution.

In your case, a `"3 M"` barium chloride solution will contain `3` moles of barium chloride, `"BaCl"2`, for every `"1 L"` of solution.

As you know, solutions are homogeneous mixtures, which means that they have the same composition throughout. This implies that the molarity of the solution can be used as a conversion factor.

Since you know that `"1 L"` of this solution contains `3` moles of solute, you can scale up this known composition to determine the number of moles of solute present in `"6.5 L"` of solution

`6.5 color(red)(cancel(color(black)("L solution"))) * overbrace("3 moles BaCl"_2/(1color(red)(cancel(color(black)("L solution")))))^(color(blue)("= 3 M")) = color(darkgreen)(ul(color(black)("20 moles BaCl"_2)))`

The answer is rounded to one significant figure, the number of sig figs you have for the molarity of the solution.