Question #1f4d1

1 Answer
Stefan V.
Sep 22, 2016

About #"34 g"#.

Explanation:

You can solve this problem by looking at the solubility graph for potassium nitrate, #"KNO"_3#.

www.mts.net

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"#

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

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

You can now use this solubility to figure out how many grams of potassium nitrate can be dissolved in #"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.

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