acid-base chemistry special double replacement reactions
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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
• 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
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 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
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
Titration-• Slowly adding a solution of known concentration
to one of unknown concentration until a neutral solution is formed.
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