Question

Question #73d8e

Answer 1

`"185 g H"_2"O"`

Explanation:

The solubility of sodium chloride in water tells you how many grams of sodium chloride can be added per `"100 g"` of water in order to get a saturated solution of sodium chloride at a given temperature.

You know that at `20^@"C"`, a saturated solution of sodium chloride will contain `"36.0 g"` of salt per `"100. g"` of water.

Since a solution is a homogenous mixture, i.e. it has the same composition throughout, you can use the solubility of the salt at this temperature as a conversion factor to determine how many grams of water would be needed to make a saturated solution of sodium chloride that contains `"66.5 g"` of solute.

`66.5 color(red)(cancel(color(black)("g NaCl"))) * overbrace(("100. g H"_2"O")/(36.0color(red)(cancel(color(black)("g NaCl")))))^(color(blue)("the solubility of the salt at 20"^@"C")) = color(darkgreen)(ul(color(black)("185 g H"_2"O")))`

The answer is rounded to three sig figs, the number of sig figs you have for your values.

You can thus say that at `20^@"C"`, a saturated solution of sodium chloride, which is a solution in which the undissolved solid is in equilibrium with the solvated ions, contains `"66.5 g"` of sodium chloride per `"185 g"` of water.