Question #3501f

1 Answer
Stefan V.
Mar 7, 2017

"20 moles BaCl"_220 moles BaCl2

Explanation:

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

In your case, a "3 M"3 M barium chloride solution will contain 33 moles of barium chloride, "BaCl"2BaCl2, for every "1 L"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"1 L of this solution contains 33 moles of solute, you can scale up this known composition to determine the number of moles of solute present in "6.5 L"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.

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