Chapter 1, Problem 1.74AE

Potassium sulfate has a solubility of 15 g/ 100 g water at 40C. A solution is prepared by adding 39.0 g of potassium sulfate to 225 g of water, carefully heating the solution, and cooling it to 40C. A homogeneous solution is obtained. Is this solution saturated, unsaturated, or supersaturated? The beaker is shaken, and precipitation occurs. How many grams of potassium sulfate would you expect to crystallize out?

Decide whether each of the following is a physical property or a chemical property of the substance. a Salt substitute, potassium chloride, dissolves in water. b Seashells, calcium carbonate, fizz when immersed in vinegar. c The gas hydrogen sulfide smells like rotten eggs. d Fine steel wool (Fe) can be burned in air. e Pure water freezes at 0C.

How do you distinguish (a) chemical properties from physical properties? (b) distillation from filtration? (c) a solute from a solution?

Aspirin is a pure substance. If you had the choice of buying a widely advertised brand of aspirin whose effectiveness is well known or the generic product of a new manufacturer at half the price, which would you buy? Explain.

Table salt from the beaker on the left in the photograph is added to water, forming the solution on the right of the photo. If you want to separate the mixture, would the distillation apparatus in figure 2-16 or the filtration apparatus in figure 2-17 be the better choice? Explain.

You are given a hammer, a battery, a bulb, wires and switch.(a) How could you use them to distinguish between samples of metals and non- metals?(b) Asses the usefulness of these tests in distinguishing between metals and non-metals?

What are the answers in the gaps?

7. State whether each of the following represents a chemical change or merely a physical change:(a) A few grams of sucrose (table sugar) are placed in a small beaker of deionized water; the sugar crystals “disappear,” and the liquid in the beaker remains clear and colorless.(b) A copper statue, over time, turns green.(c) When a teaspoon of baking soda (sodium bicarbonate) is placed into a few ounces of vinegar (acetic acid), volumes of bubbles (effervescence) are produced.

Select the best answer or answers from the choices given: Which of the following does not describe a mixture? (a) properties of its components are retained, (b) chemical bonds are formed, (c) components can be separated physically, (d) includes both heterogeneous and homogeneous examples.