Question

Question #a69e3

Answer 1

`"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)|)))`