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Research Question: How does the solubility of potassium nitrate change with respect to the change in temperature by 20C keeping the pressure and the nature of the solute and solvent constant?

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CHEMISTRY LABORATORY REPORT To investigate the solubility of ionic compounds. Design Nikita Bansal B.D.Somani International School Chemistry Standard Level Candidate Number- 002602015 Session: May 2010 Aim: To investigate the solubility of Ionic Compounds Research Question: How does the solubility of potassium nitrate change with respect to the change in temperature by 20�C keeping the pressure and the nature of the solute and solvent constant? Hypothesis: An Ionic Compound is a chemical compound in which ions are held together in a lattice structure by ionic bonds. Ionic bonding occurs between elements that have a large difference in their electronegativities. In this bonding, a metal loses electrons to form a positively charged ion (cation) and a non- metal gains an electron to forma positively charged ion (anion). The compounds formed due to ionic bonding are held together due to a strong electrostatic force of attraction. Solubility is a result of an interaction between polar water molecules and the ions which make up a crystal. ...read more.


The temperature ranges from 20 to 100c and thus we can see that the solubility increases. The above diagrams show that an increase in temperature will lead to an increase in the solubility of potassium nitrate. The solubility of solutes is dependent on temperature. When a solid dissolves in a liquid, a change in the physical state of the solid takes place. Heat is required to break the bonds holding the molecules in the solid together. At the same time, heat is given off during the formation of new solute -- solvent bonds. If the heat given off in the dissolving reaction is less than the heat required to break apart the solid, the net dissolving reaction is endothermic (energy required). The addition of more heat facilitates the dissolving reaction by providing energy to break bonds in the solid. This is the most common situation where an increase in temperature produces an increase in solubility for solids. This is what will occur in the heating of the potassium nitrate and therefore the solubility will increase. ...read more.


7. After the crystallization temperature has been recorded, put the test tube back into the water bath and warm the solution until all of the crystals have re dissolved. Repeat the cooling procedure to check the crystallization temperature. The two readings should be within 1 degree of each other. If the two readings do not agree within 1 degree, re warm the solution in the water bath, cool it, and continue until satisfactory agreement is obtained. 8. Record sample mass and then record the experimental temperature next to it. 9. Repeat the experiment two to three times to ensure accuracy. Precautions: - Handle hot equipment and solutions cautiously. - The thermometer bulb is fragile; handle gently Apparatus 1. 1 0.5 dm3 beaker 2. 1 iron ring 3. 1 wire gauze 4. 0.3dm3 tap water 5. 5g Potassium Nitrate 6. 2 Test tubes along with test tube holder 7. Stirring wire 8. Thermometer 9. Bunsen Burner 10. Water Bath Data Table KNO3 Solubility Temperature 20 40 60 80 100 ?? ?? ?? ?? Nikita Bansal Chemistry Standard Level ...read more.

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