How to Increase the Solubility of an Ionic Compound in Water
An ionic compound dissociates into ions (charged particles) in the solution. A classic example of ionic compounds is inorganic salts, such as sodium chloride (NaCl) or potassium nitrate (KNO3). The solubility characterizes how well a substance dissolves in solvent and is typically expressed in grams of the dissolved compound per 100 g of solvent. As a rule (with a few exceptions) the solubility of ionic compounds in water increases with temperature. To illustrate this principle, prepare the solution of potassium nitrate by dissolving 120 g of the salt in 200 ml of water.
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Instructions
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1
Divide the mass of the salt by the mass (volume) of water, and multiply the quotient by 100 to calculate solubility that is required to make the particular solution. In our example, it is (120 / 200) x 100 = 60 g/100 g water.
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2
Find solubility of the compound in question (see the Solubility Database link in Resources). In our example, the solubility of potassium nitrate is 31.6, 61.3 and 106 g /100 g water at temperatures 20, 40 and 60 degrees C, respectively. Hence the solution must be heated to at least 40 C to achieve the required salt solubility of 60 g/100 g (from Step 1).
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3
Pour water (200 ml in our example) into a metal pan and heat it to 40 to 50 degrees C, monitoring the temperature with the thermometer.
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4
Weigh potassium nitrate (120 g in our example) on a scale and place in the warm water from Step 3.
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5
Stir the solution for 2 to 4 minutes with a spoon to dissolve the salt.
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