Question #3501f

1 Answer
Stefan V.
Mar 7, 2017

#"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.

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