Question #a69e3

1 Answer
Stefan V.
May 5, 2016

#"30% m/m"#

Explanation:

A solution's percent concentration by mass, #"%m/m"#, essentially tells you how many grams of solute you get in #"100 g"# of solution.

This means that in order to find a solution's percent concentration by mass, you must determine how many grams of solute you have in #"100 g"# of solution.

In your case, the solution is said to contain #"90 g"# of calcium iodide, #"CaI"_2#, which is your solute, and have a total mass of #"300 g"#.

This means that #"100 g"# of solution will contain

#100 color(red)(cancel(color(black)("g solution"))) * "90 g CaI"_2/(300color(red)(cancel(color(black)("g solution")))) = "30 g CaI"_2#

So, if #"100 g"# of solution contains #"30 g"# of solute, it follows that its percent concentration by mass will be equal to

#"% m/m" = color(green)(|bar(ul(color(white)(a/a)"30%"color(white)(a/a)|)))#

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