Chapter 11

Water and Solutions

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Homework for Chap 11Homework for Chap 11

Read p 275 – 280; 283 - 293

Applying the Concepts # 1 - 21;

27 - 30, 32, 33, 37 - 49

Properties of Water

• Aqueous solutions ≡ solids, liquids, or gasesdissolved in water

• Household water:

• Drinking/cooking 2 %• Washing dishes 6 %• Laundry 11%• Bathing 23%• Toilets 29%• Lawns/gardening 29%

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

Types of Solutions

• Unsaturated solution - can dissolve more solid

• Saturated solution – holds all the solid it can at agiven temperature

• Supersaturated solution – hold more solid that normal ata given temperature

There is a limit to how much solid can dissolve in a liquid

Fig 11.9 Solubility change with temperature

Fig 11.5 Structural formula of a soap molecule

Fig 11.6 NaCl dissolving in water

Hydration - process in which an ion is surrounded by water molecules arranged in a specific

manner.

NaClNaCl CHCH33OHOH

NaClNaCl CHCH33OHOH

H2O is a polar molecule

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

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

nonelectrolyte weak electrolyte strong electrolyte

Electrolyte Properties

Figure 4.2

Strong Electrolyte – 100% dissociation

NaCl (s) Na+ (aq) + Cl- (aq)H2O

Weak Electrolyte – not completely dissociated

CH3COOH CH3COO- (aq) + H+ (aq)

Conduct electricity in solution?

Cations (+) and Anions (-)

Fig. 11.11 The reaction of water and hydrogen chloride

Hydronium ion

Fig 11.13 Dissolving a mole of a compound in water

1 mole sucrose → 1 mole of molecules

1 mole NaCl → 2 moles of ions

1 mole CaCl2 → 3 moles of ions

Strong Electrolytes Are…

Strong acids

Strong bases

Soluble ionic salts

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)

Based on powers of 10:

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

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

Fig. 11.16 Common substances that are acidic

citric acidascorbic acid

acetic acid

carbonic acid

citric acidascorbic acid

Table 11.5Approximate pH of some common substances

Acids, Bases, and Salts

acid + base salt + water

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

A Neutralization Reaction: