June 2010 Chemistry Regents #65-68

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Base your answers to questions 65 through 68 on the information below.

In a laboratory, a student makes a solution by completely dissolving 80.0 grams of KNO3(s) in 100.0 grams of hot water. The resulting solution has a temperature of 60.C. The room temperature in the laboratory is 22C.

65 Classify, in terms of saturation, the type of solution made by the student. [1]

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unsaturated

NOTE= look at Table G

KNO3 holds 115g at 60.C

66 Compare the boiling point of the solution at standard pressure to the boiling point of water at standard pressure. [1]

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The boiling point of the solution at standard pressure is higher than the boiling point of waterat standard pressure.

Water boils at a lower temperature.

Link-Boiling point elevation

67 Describe the direction of heat flow between the solution made by the student and the air in the laboratory. [1]

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NOTE=Energy (heat) flows from hot to cold

Heat flows from the solution to the air in the laboratory.

The air gains heat from the solution.

68 Describe a laboratory procedure that can be used to recover the solid solute from the aqueous solution. [1]

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Gently heat the solution to evaporate the water until only solid KNO3 remains.

Boil off the water.

Distillation

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