Chapter 11

Water and Solutions

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Homework for Chap 11Homework for Chap 11

Read p 275 – 280; 284 - 290

Applying the Concepts # 1 – 3; 9 - 24

Fig. 11.2 (A) The water molecule is polar (It has a dipole.)

H2O

Fig. 11.2 (B) Attractions between water molecules

Ice is less dense than water

Water is a Unique Substance:

Fig. 11.3 The hexagonal structure of ice

Maximum Density4 °C

Density of Water

Fig. 11.4 The density of water just above its freezing point

Solution - a homogenous mixture of 2 or more substances

Solute - the substance(s) present in the smaller amount(s)

Solvent - the substance present in the larger amount

Solution Solvent Solute

Soft drink (l)

Air (g)

Soft Solder (s)

H2O

N2

Pb

Sugar, CO2

O2, Ar, CH4

Sn

Fig 11.6 NaCl dissolving in water

Fig. 11.10 Behavior of electrolytes and nonelectrolytes.

Electrolyte - a substance that, when dissolved in water, forms a solution that can conduct electricity.

Nonelectrolyte - a substance that, when dissolved, forms a solution that does not conduct electricity.

nonelectrolytestrong electrolyte

Fig. 11.11 The reaction of water and hydrogen chloride

Hydronium ion

Acids, Bases, and Salts

acid + base salt + water

HCl (aq) + NaOH (aq) NaCl (aq) + H2O

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Acids

1. Have a sour taste. e.g., Vinegar, lemons, limes, sour milk

2. Cause litmus to change from blue to red.

4. Acid solutions conduct electricity.

3. Acids neutralize bases.

Fig 11.14 (A)

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1. Have a bitter taste. e.g., caffeine, walnuts, soap

3. Feel slippery. Many soaps contain bases.

Bases

5. Basic solutions conduct electricity.

2. Cause litmus to change from red to blue.

4. Bases neutralize acids.

Fig 11.14 (B)

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How do we express the concentration

of an acid or a base?

pH scale – based on concentration of the

hydronium ion (H3O+)

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

acidic basicneutral

Based on powers of 10:

e.g., a soln with pH = 3 is 10 times moreacidic than a solution with pH = 4

Fig. 11.16 Common substances that are acidic

Table 11.5Approximate pH of some common substances