Acid-Base Chemistry

Special Double Replacement Reactions

15.2 & 15.3The Nature of Homogeneous and Heterogeneous Systems

Homogeneous Systems – Solutions• Aqueous- water containing dissolved substance(s)

(note: not all solutions are aqueous)• Solvent- “does the dissolving”• Solute- “is dissolved”

Heterogeneous Systems – Colloids and Suspensions

• Contains a dispersed phase in a dispersion medium

• Particles in colloids and suspensions are larger than solute particles

Property Solution Colloid Suspension

Particle Size 0.1-1nm 1-1000nm 1000nm or larger

Particles Settle? No No Yes

Tyndall Effect? No Yes Yes

Type of Mixture Homogeneous Heterogeneous Heterogeneous

Solutions, Colloids and Suspensions

Characteristics of Heterogeneous Mixtures

• The Tyndall Effect• Scattering of visible light by particles

• Brownian Motion• Particles exhibiting the Tyndall Effect move

erratically. This movement is caused by the collision of the dispersed particles with the molecules in the media.

Characteristics of Heterogeneous Mixtures

• Coagulation• Colloidal particles adsorb charged particles from the

surrounding media. Repulsion between like charged particles keeps particles from settling.

• Emulsions• Colloidal dispersion of a liquid in a liquid.

Know examples from table 15.3 on page 460

What is Dissolving?

• Term for solute particles being surrounded by solvent molecules = Solvation

Properties of Solutions16.1 and 16.2

Solubility Concentration

• Rate of dissolving- influenced by:

Agitation, temperature, particle size (surface area)

Factors Influencing Dissolving

• Amount that can be dissolved- influenced by:

Temperature/Pressure

Solubility Curves

• Solubility- the maximum amount of solute per a given amount of solvent (usually 100g water)

Types of Solutions

Unsaturated Solution of NaNO3

Supersaturated Solution of NaNO3

Saturated Solution of NaNO 3

Interpreting Solubility Curves

• Solids in water- generally more soluble at higher temperatures (note: Na2SO4)

• Gases in water- solubility decreases with increased temperature

Concentrated vs. Dilute

Concentrated Sugar Solution Dilute Sugar Solution

Solution Concentration

• Molarity= moles of solute per Liters of solution (M=n/V)

Example: Calcuate the molarity when 75.0 grams of MgCl2 is dissolved in 500.0 mL of solution.

Practice

• Determine the molarity of the following solutions:

– 120. grams of calcium nitrite in 240.0 mL of solution. • 3.79 M

– 98.0 grams of sodium hydroxide in 2.2 liters of solution.

• 1.1 M

– How many grams of solid are required to make

0.75 L of 0.25 M Na2SO4

• Dissolve 27 g Na2SO4, dilute to 0.75 L

Dilution of Solutions:

• M1V1= M2V2

(note: moles of solute remain constant)

• Example: How many mL of a 5.0M stock solution would you need to prepare 100.0mL of 0.25M H2SO4?

– 5.0 mL

Practice

• If I have 340 mL of a 0.50 M NaBr solution, what will the concentration be if I add 560 mL more water to it? – 0.19 M

• To what volume would I need to add water to the solution in the previous problem to get a solution with a concentration of 0.0250 M?– 6800mL

Percent Solution

• Percent by Mass– %mass= (mass of solute/mass of solution)*100– What is the percent by mass of NaHCO3 in a solution

of 20g NaHCO3 in 600 g of solution?

• Percent by Volume (both solute and solvent are liquids)

– %volume = (volume of solute/volume of solution)* 100– If you have 100.0 mL of a 30.0% ethanol solution,

what volumes of ethanol and water are in the solution?

Acids and Bases19.1-19.4

Acids and BasesAcids Bases

Taste Sour Bitter

Feel Irritating (burning) Slippery

React with metals Produce H2 gas NR

Change indicator Colors?

Yes Yes

Characteristic Formula

H in front or COOH at end

OH at the end

Types of Acids

• Mono-, di-, and triprotic acids- have 1, 2, or 3 H atoms that can become ionized

(note: not all compounds that contain H are acidic and not all hydrogens in an acid will necessarily ionize)

Recall Naming Rules for:

Binary Acids (HCl) Hydro _______ ic Acid

Oxyacids (H2SO4) - ic acids from ate ions

- ous acids from ite ions

Arrhenius Definition of Acids • Acids- generate H+ ions in water• Bases-generate OH- ions in water

Measuring pH• pH = -log[H+]

Acidic SolutionspH <7, [H+] >1x 10-7

Neutral SolutionspH =7, [H+] =1x 10-7

Basic SolutionspH >7, [H+] <1x 10-7

Strong vs. Weak

• Strong acids– HCl– HBr– HI

– HClO4

– HNO3

– H2SO4

• Strong Bases– Group I or IIA with OH

Determined by the extent of ionization

Small dissociation constants (Ka or Kb) = weak acids and basesLarge dissociation constants = strong acids and bases

Neutralization Reactions-

• Acid and base react to yield water and a salt

Titration-• Slowly adding a solution of known concentration

to one of unknown concentration until a neutral solution is formed.

Acid-Base Indicators• Used to predict endpoint of titration• An acid or base that undergoes dissociation in a known pH range• An indicators acid and base form have different colors