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The solubility of Potassium Nitrate lab report.

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The solubility of Potassium Nitrate lab report.

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The Solubility of Potassium Nitrate


The aim of this experiment is to find out by how much the solubility of potassium nitrate into distilled water increases when the solution is heated, and if yes, by how much.


According to data on the internet, 3.75 × 10­¹ moles of potassium nitrate dissolve in 100g of water. I believe this information may be correct. I also believe that as the solute is absorbing outside heat, the energy is increased causing it to dissolve both faster, with more potassium nitrate.


Bunsen burner

25g Potassium nitrate

Distilled water

Boiling tube




1) Weigh out 25g Potassium Nitrate into a boiling tube.

2) Add 10ml water

3) Heat solution over bunsen until potassium nitrate dissolves, moving the tube in and out of the flame so it doesn't boil over.

4) Allow to cool and record temperature at which crystals appear

5) Add 5ml of water and repeat steps 3) and 4)

6) Repeat step 5) until you have 30ml of water in the boiling tube

7) Transform data so it is expressed as a mass of potassium nitrate per 100g of water.

8) Graph


Water (ml)Temp at which crystals appear ( C)Potassium Nitrate (g) per 100g of water






Mass of potassium nitrate dissolved at 40 : 64g

Mass of potassium nitrate dissolved at 80 : 169g

Mass obtained as crystals when solution cooled from 80 to 25 : 134g or 79.3%

Two graphs: one from the internet, one made according to our results.


From the results we can see that the solubility of potassium nitrate is increased as the temperature is increased. The relationship is nonlinear, which means it doesn't form a straight line when plotted on a graph. Now, there are three main factors, which affect solubility (besides pressure).

Temperature will affect solubility. If the solution process absorbs energy then the solubility will be...