Potassium Nitrate Solubility Essay

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Abstract: The effect of temperature on solubility of potassium nitrate was demonstrated. This was done by dissolving the salt in distilled water at different concentrations and finding the temperature at which crystallisation occurred. From this a solubility curve could be formed. It was found that as the temperature increased, so did the solubility of potassium nitrate in distilled water. At 50C our results indicated a solubility of 89 g/100mL of H2O which was close to the known solubility of 80 g/100mL. Introduction: When a salt, such as potassium nitrate or sodium chloride, is placed in water a dissolving reaction will occur. At first, the positive and negative ions of the salt compound are only attracted to each other. In order for the salt to dissolve, these bonds must be broken so that the ions disassociate from each other. In the water molecules, hydrogen is slightly positive and oxygen slightly negative so they are attracted to ions of the opposite charge, known as dipole attraction. These water molecules break apart the bonds of a salt by surrounding themselves around the salt ions, with the opposite charges facing each other. Whether or not a salt dissolves is determined by which attractive force is stronger, the internal ionic force or the attraction for the ions from the water molecules (Ophardt, C., 2003). Potassium nitrate (KNO3) contains negative nitrate ions and positive potassium ions. When potassium nitrate is placed in water the slightly positive hydrogen’s in the water molecule are attracted to the nitrate ions and the potassium ions are attracted to the slightly negative oxygen. Figure 1 shows how sodium chloride would bond when placed in water. Figure 1 Sodium chloride dissolved in water (Adams, R. et al, 2011) The solubility of a solute in a solvent is affected largely by the temperature. A solubility curve (as seen in Figure 2)

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