“I would sooner fail than not be among the greatest.” ~John Keats

Name: ______Date: ______UNIT 6: SOLUTIONS AND GASES 6.4 Independent Practice (12 pts) 1. What is the molarity of a 500 L solution containing 5.5 moles of KI?

2. What is the molarity of a solution that contains 4.0 mol of NaOH in 0.50 L of solution?

3. A swimming pool reports that chlorine is present at 20 g in 100 g of water. Express this in terms of parts per million. (ppm)

4. How many moles of magnesium chloride (MgCl2) are needed to make 6.0 L of a 3.0 M solution?

5. How many grams of CaCl2 would be required to produce a 3.5 M (molar) solution with a volume of 2.0L?

Directions: Read the passage below and answer the accompanying questions CONCENTRATION 1 .What does dilute mean? Consider saltwater. Concentrated saltwater can be used to rinse the mouth, but only dilute saltwater can be used to rinse the eyes. You would not want to confuse the two. Concentration matters. A common measure of concentration is humidity. Humidity is the measure 2. Why would not want to of the amount of water in air, and relative humidity is the amount of water confuse the two currently in the air compared to the maximum amount of water that the air could concentrations? hold at that same temperature and pressure. When it comes to chemical reactions, it is more meaningful to talk about molecules per liter than grams per liter. To understand why, consider the following two statements. Which is more useful for calculating staff requirements if the teacher/student ratio needs to be maintained 3. What is humidity? at twenty to one? There are 11,756 kilograms of students in the new freshman class Or There are 190 students in the new freshman class. 4. Which of the two statements Chemists characterize the concentration of a solution by a measure of the number in the passage in more of molecules per volume rather than the number of grams per volume because meaningful? Explain why. reactions happen when one molecule reacts with one molecule, not when one gram reacts with one gram. The difficulty is that molecules are very small, and a good many of them are required to make up a measureable amount. For instance, it requires about a trillion trillion water molecules in the liquid state to fill a 240-mL 5. Why do chemists “I would sooner fail than not be among the greatest.” ~John Keats

(one-cup) container. Therefore, it is infinitely easier to speak of collections of characterize the concentration molecules rather than individual molecules. The name that chemists agreed on for of a solution by a measure of # a collection of molecules is a mole, and a mole is like a dozen—only different. of molecules per volume rather A dozen indicated a number of things, such as twelve eggs. A mole than # of grams per volume? indicates a number of things: a mole is 6.023 hundred billion things, an almost unimaginably huge number!!! WHAT BODY, WHAT AROMA, WHAT CHEMISTRY The making of wine involves chemistry on many levels. For instance, wine- makers and wine tasters rely on concentration properties to make and describe their…how shall we say…delicate, yet somewhat bold and enticing, product. Professional wine tasters use a number of interesting terms such as 6. What is a mole? (REVIEW) buttery, chewy, and fruity to describe the characteristics of wines, which include aroma, texture and body. It is this last characteristic, body, that connects with the subject of this lesson: concentration. Body is the perceived density of the wine in the mouth and depends in good part on the amount of alcohol in the wine. Density, related to concentration, plays a vital part in wine making, too. 7. Why is concentration The grape juice and crushed fruit is the beginning part, ready to be important in wine-making? fermented. Fermentation is the process where certain yeasts consume sugar and produce ethanol (alcohol) and carbon dioxide. Too little sugar leads to too little alcohol, and too much sugar changes the nature of the wine. So as we have seen, measurement and control of concentration is critical in chemistry as well as wine or saltwater.

HOMEWORK (10 pts) 1. Determine the molarity of 500 mL of a solution with 0.35 mol of dissolved solute.

2. A 200 mL sample of a solution contains 4.0 g of NaOH. What is its molarity?

3. What is the molarity of a 500 L solution containing 249 g of KI?

4. How many moles of LiF would be required to produce a 2.5 M solution with a volume of 1.5 L?

5. How many grams of KNO3 are present in 250 mL of 2.0 M potassium nitrate solution? “I would sooner fail than not be among the greatest.” ~John Keats