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Chapter 7 Solutions and Colloids

7.2 Solubility

Copyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings

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Solubility is

• the maximum amount of solute that dissolves in a specific amount of solvent.

• expressed as grams of solute in 100 grams of solvent water.

g of solute

100 g water

Solubility

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Unsaturated Solutions

Unsaturated solutions

• contain less than the maximum amount of solute.

• can dissolve more solute. Dissolved solute

Copyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings

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Saturated Solutions

Saturated solutions

• contain the maximum amount of solute that can dissolve.

• have undissolved solute at the bottom of the container.

Copyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings

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Supersaturated Solutions

Supersaturated solutions

• An unstable solution that contains an amount of solute greater than the solute solubility.

• Also has undissolved solute at the bottom of the container.

Copyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings

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At 40C, the solubility of KBr is 80 g/100 g H2O.Identify the following solutions as either1) saturated or (2) unsaturated. Explain.

A. 60 g KBr added to 100 g of water at 40C.

B. 200 g KBr added to 200 g of water at 40C.

C. 25 g KBr added to 50 g of water at 40C.

Learning Check

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A. 2 Amount of 60 g KBr/100 g water is less than the solubility of 80 g KBr/100 g water.

B. 1 In 100 g of water, 100 g KBr exceeds the solubility of 80 g KBr water at 40C.

C. 2 This is the same as 50 g KBr in 100 g of water, which is less than the solubility of 80 g

KBr/100 g water at 40C.

Solution

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Effect of Temperature on Solubility

Solubility• Depends on

temperature.• Of most solids

increases as temperature increases.

• Of gases decreases as temperature increases.

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A. Why could a bottle of carbonated drink possibly burst (explode) when it is left out in the hot sun ?

B. Why do fish die in water that is too warm?

Learning Check

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A. The pressure in a bottle increases as the gas leaves solution as it becomes less soluble at high temperatures. As pressure increases, the bottle could burst.

B. Because O2 gas is less soluble in warm water, fish cannot obtain the amount of O2 required for their survival.

Solution

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Solubility and Pressure

Henry’s Law states • the solubility of a gas

in a liquid is directly related to the pressure of that gas above the liquid.

• at higher pressures, more gas molecules dissolve in the liquid.