Question #1f4d1

1 Answer
Sep 22, 2016

About "34 g"34 g.

Explanation:

You can solve this problem by looking at the solubility graph for potassium nitrate, "KNO"_3KNO3.

![www.mts.net](useruploads.socratic.org)

For starters, the temperature is given to you in Kelvin, so convert it to degrees Celsius

t[""^@"C"] = "313 K" - "273.15 K" ~~ 40^@"C"t[C]=313 K273.15 K40C

Now, according to the solubility graph, potassium nitrate has a solubility of about "67 g/100 g H"_2"O"67 g/100 g H2O. This means that in order to have a saturated solution of potassium nitrate at 40^@"C"40C, you must dissolve about "67 g"67 g of this salt in "100 g"100 g of water.

In other words, an aqueous solution of potassium nitrate will contain a maximum of "67 g"67 g of dissolved potassium nitrate for every "100 g"100 g of water at 40^@"C"40C.

You can now use this solubility to figure out how many grams of potassium nitrate can be dissolved in "50 g"50 g of water at this temperature to have a saturated solution

50 color(red)(cancel(color(black)("g H"_2"O"))) * "67 g KNO"_3/(100color(red)(cancel(color(black)("g H"_2"O")))) = "34 g KNO"_3

I'll leave the answer rounded to two sig figs.