Chemistry Homework #8- Pg 82

Pg 82 #1-8

1.     Three teaspoons of sugar will completely dissolve in a serving of hot tea, but not completely dissolve in iced tea because when there is a higher temperature, the water can hold more of a substance, which is called a saturated solution, while in iced tea, the temperature is colder and it is harder for the substance to fully dissolve, which causes an unsaturated solution because it holds less substance than it would at that normal temperature.

2.     The maximum mass of potassium chloride that will dissolve in 100 grams of water at 70 degrees Celsius is about 49 grams.

3.     A. The maximum amount of sugar that will dissolve in 100 mL of water is 200 grams

B. The maximum amount of sugar that will dissolve in 355 mL of water is 710 grams.

C. The maximum amount of sugar that will dissolve in 946 mL of water is 1,892 grams

4.     A. 20 degrees Celsius: Sodium chloride, Potassium chloride, Potassium nitrate

B. 80 degrees Celsius: Potassium nitrate, Potassium chloride, Sodium chloride

5.     SATURATED: if you continue adding a substance without adding more water, eventually crystals will remain undissolved, as a solid, on the bottom of the container no matter how long you vigorously stir.

UNSATURATED: a solution that contains less dissolved solute than the amount that the solvent can normally hold at that temperature.

6.     A. The maximum mass of Potassium nitrate that can dissolve in 100 grams of water if the water is at 20 degrees Celsius is 30 grams.

B. At 30 degrees Celsius, 55 grams of Potassium nitrate is dissolved in 100 grams of water. This solution is supersaturated.

C. A saturated solution of Potassium nitrate is formed in 100 grams of water at 75 degrees Celsius. If some of the solute precipitates as the saturated solution cools to 40 degrees Celsius, the mass of solid Potassium nitrate that should form is 60 grams.

7.     If you are given a solution of Potassium nitrate of unknown concentration, if a potassium nitrate crystal is added to a:

A.     Unsaturated solution: it can go into solution

B.     Saturated solution: it will fall to the bottom of the container or become supersaturated.

C.     Supersaturated solution: any crystals that are more than the solution should hold will all fall down to the bottom of the container.

8.     The percent concentration of the ethanol, expressed as percent ethanol by mass is about 23%.