# The solubility of Potassium Nitrate lab report.

Essay by dark_emperor87High School, 10th gradeA+, November 2003

The Solubility of Potassium Nitrate

Aim:

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.

Hypothesis:

According to data on the internet, 3.75 ÃÂ 10ÃÂ­ÃÂ¹ 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.

Apparatus:

Bunsen burner

25g Potassium nitrate

Distilled water

Boiling tube

Clamp

Thermometer

Method:

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

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

Results:

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

10101250

1599166.6

2097125

2595100

309383.3

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.

Conclusion:

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...