Question

Principles of Inorganic Chemistry! Week 5 Effect of Temperature on Solubility of a Salt In this experiment, you will study the effect of changing temperature on the amount of solute that will dissolve in a given amount of water. Water solubility is an important physical property in chemistry, and is often expressed as the mass of solute that dissolves in 100 g of water at a certain temperature. In this experiment, you will completely dissolve different quantities of potassium nitrate, KNOs, in the same volume of water at a high temperature. As each solution cools, you will monitor temperature using a Temperature Probe and observe the precise instant that solid crystals start to form. At this moment, the solution is saturated and contains the maximum amount of solute at that temperature. Thus each data pair consists of a solubility value (g of solute per 100 g H2O) and a corresponding temperature. A graph of the temperature solubility data, known as a solubility curve, will be plotted using LabQuest. OBJECTIVES In this experiment, you will . Study the effect of changing temperature on the amount of solute that will dissolve in a given amount of water. • Plot a solubility curve. MATERIALS LabQuest Temperature Probe ring stand four 20 x 150 mm test tubes test tube rack hot plate 400 ml beaker 10 ml graduated cylinder 250 ml beaker ring stand 2 utility clamps stirring rod potassium nitrate, KNO, PROCEDURE 1. Obtain and wear goggles. 2. Label four test tubes 1-4. Into each of these test tubes, measure out the amounts of solid shown in the second column below (amount per 5 mL). Note: The third column (amount per 100 g of H2O) is proportional to your measured quantity, and is the amount you will enter for your graph in Step 8. Test tube Amount of KNO, number used per 5 mL H2O (weigh in Step 2) 1 2.0 24.0 3 6.0 4 8.0 Amount of KNO, used per 100 g H.O (uso in Step 10) 40 80 120 160 Chemistry with Vernier

Answer 1

1) The best line is drawn:

Solubility - 0.46*x + 3.7 Temperature 23.9 36.7 61.1 77.1 50 100 125 150

2) As the temperature increases, the solubility of KNO3 increases.

3) The cases are answered:

a) Saturated solution, at that temperature only dilute 80 g of KNO3.

b) Unsaturated, at this temperature, it can dilute more than 60 g.

c) Unsaturated, at that temperature and volume, more than 140 g can be dissolved.

4) Yes, they can be diluted, up to 100 g.

5) No, you can only dilute about 80 g.

6) At this temperature, 60 g can be diluted.

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