Chapter 11 Water and Solutions

3 Homework for Chap 11 Read p 275 – 280; Applying the Concepts # ; , 32, 33,

Properties of Water Aqueous solutions ≡ solids, liquids, or gases dissolved in water Household water: Drinking/cooking 2 % Washing dishes 6 % Laundry 11% Bathing23% Toilets 29% Lawns/gardening29%

Fig (A) The water molecule is polar (It has a dipole) H2OH2O Fig (B) Attractions between water molecules

Ice is less dense than water Water is a Unique Substance: Fig The hexagonal structure of ice

Maximum Density 4 °C Density of Water Fig 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 SolutionSolventSolute Soft drink (l) Air (g) Soft Solder (s) H2OH2O N2N2 Pb Sugar, CO 2 O 2, Ar, CH 4 Sn

Types of Solutions Unsaturated solution - can dissolve more solid Saturated solution – holds all the solid it can at a given temperature Supersaturated solution – hold more solid that normal at a given temperature There is a limit to how much solid can dissolve in a liquid

Fig 11.9 Solubility change with temperature

Fig 11.5Structural 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. NaCl CH 3 OH

NaCl H 2 O 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) H2OH2O Weak Electrolyte – not completely dissociated CH 3 COOH CH 3 COO - (aq) + H + (aq) Conduct electricity in solution? Cations (+) and Anions (-)

Fig The reaction of water and hydrogen chloride Hydronium ion

Fig Dissolving a mole of a compound in water 1 mole sucrose → 1 mole of molecules 1 mole NaCl → 2 moles of ions 1 mole CaCl 2 → 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 (A)

22 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 (B)

Based on powers of 10: e.g., a soln with pH = 3 is 10 times more acidic 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 (H 3 O + ) acidicbasicneutral

Fig Common substances that are acidic citric acid ascorbic acid acetic acid carbonic acid citric acid ascorbic acid

Table 11.5 Approximate pH of some common substances

Acids, Bases, and Salts acid + base salt + water HCl (aq) + NaOH (aq) NaCl (aq) + H 2 O A Neutralization Reaction: