The graph below shows how the solubilities of 4 substances are affected by changes in temperature. From the graph we can see that at 50^oC approximately 70 grams of potassium nitrate (KNO₃) will dissolve in 100 grams of water.
Sodium chloride = NaCl, potassium sulfate = K₂SO₄, potassium nitrate = KNO₃

1) What is the maximum amount, in grams, of substance "X" that can dissolve in 100 grams of water at 50^oC?

2) What is the maximum amount, in grams, of substance "X" that can dissolve in 100 grams of water at 100^oC? Solution

3) Irene wanted to see how much of each substance she could dissolve in two litres of water at 50^oC. She listed the substances in order of greatest mass to the least mass dissolved.
The correct order was X, potasium nitrate, potassium sulfate, sodium chloride X, potassium nitrate, sodium chloride, potassium sulfate sodium chloride, potassium sulfate, X, potassium nitrate

4) Stephen dissolved potassium nitrate into 2 litres (2,000 grams) of water at 75^oC until no more could dissolve. He presented the solution to Jonathon and asked him to guess the mass of potassium nitrate dissolved in 2 litres of water.
Jonathon quickly took out a thermometer and a calculator and after a few simple calculations gave the answer as 140 grams 2.8 kilograms 1.4 kilograms 300 grams 1.5 kilograms Solution

5) Try this advanced problem. Irene added substance "X" to 100 grams of water at 50^oC until no more could dissolve. She left the solution on a bench to cool. She returned after a few hours and noticed that the solution had cooled to 20^oC and solid substance "X" was deposited on the bottom of the container. She filtered the solid substance and weighed it. The mass of substance "X" that was filtered was 60 grams 20 grams 100 grams 150 grams 90 grams .Solution

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