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APPLYING SCIENTIFIC METHODS IN CHEMISTRYSOLUBILITY.•

To investigate how solubility changes as solventtemperature changes, Lisa first put 100 g ofwater, at O°C, in a beaker. While keeping thetemperature of the water constant, she slowlyadded the compound and stirred vigorously.Once she had added 180 g of the compound,undissolved crystals remained on the bottom ofthe beaker. Lisa filtered the mixture to reclaimthe undissolved crystals, which she dried andfound to have a mass of 2 g.

Lisa then heated the solution to 10°C. Whilestirring the solution, she added more of thecompound. After adding 10.5 g of the compound,she found that crystals remained undissolved.

Temperature (OC) Solubility (per 100g ~O)0 178

10 18720 209

30 22240 23650 26160 290

Following the same procedure as before, shereclaimed 1.5 g of crystals. Thus, 187 g of crystalshad dissolved.. Lisa repeated the procedure whileheating the solution in increments of 10°C. Herdata table is shown here.

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1. Construct a best-fit solubility curve for the compound Lisa tested by plotting her data on the graphgrid provided.

2. Based on the data, what can you conclude about the relationship between the temperature of thesolvent and the solubility of the unknown compound?

3. Looking at the shape of the curve in your graph, describe how the amount of compound that issoluble changes as the temperature increases.

4. Based on your graph, predict the solubility of the compound in water at 70°C. _

5. What kind of solution formed each time the maximum amount of compound was dissolved at a

given temperature?

6. As a result of heating in each case, what kind of solution then was formed? _

7. a. What kind of solution would be formed if Lisa allowed the solution to cool from 60°C to 50°C?

b. Would the solution be stable? _

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40 APPLYING SCIENTIFIC METHODS IN CHEMISTRY Chapter 20

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CHAPTER 16 REVIEW ACTIVITY

Date _ Class _

Text Reference: Section 16-9

Solubility Curves

Study the solubility curves in the figure, and thenanswer the questions that follow.

1. What relationship exists between solubilityand temperature for most of the substancesshown?

2. a. What is the exception?

b. What general principle accounts for this ex-ception?

3. a. Approximately how many grams of NaN03will dissolve in 100 g of water at 20°C?

b. How many grams will dissolve at 60°C?

4. How many grams of N~CI will dissolve in1 dm" of H20 at 50°C?

5. Ninety grams of NaN03 is added to 100g of H20at'O°C.With constant stirring, to what temperature.must the solution be raised to produce a saturatedsolution with no solid NaN03 remaining?

6. A saturated solution of KCI03 was made with300 g of H20 at 40°C. How much KCI03 could berecovered by evaporating the solution to dryness?

7. Five hundred grams of water is used to make asaturated solution of KCI at 10°C.How many more-grams of KCI could be dissolved if the tem-perature were raised to 100°C?

8. A saturated solution of KN03 in 200 g of H20 at50°C is cooled to 20°C. How much KN03 will pre-cipitate out of solution?

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COPYRIGHTby Prentice Hall. Inc.Reproduction of this master is restricted to duplication for classroom use only.

CHEMISTRY:The Study of Matter 16-11