Ch. 8 Solutions, Acids, & Bases I. How Solutions Form Definitions Types of Solutions Dissolving Rate of Dissolving
A. Definitions Solution – a mixture that has the same composition throughout the mixture; a homogeneous mixture Solvent Solvent – what the solute is dissolved in (in greater quantity) Solute Solute - substance being dissolved (in lesser quantity)
A. Definitions Solute Solute - KMnO 4 Solvent Solvent - H 2 O
Remember the difference between a a mixture and a compound. o Compounds have the same (fixed) composition throughout. o Mixtures can have a variable (different) composition throughout. A. Definitions
Solubility – The maximum amount of solute that can be dissolved in the solvent at a given temperature. A. Definitions
B. Types of Solutions Saturated solutions – maximum amount of solute at a given temperature. Unsaturated solutions – less than the max. amount of solute at a given temperature. Supersaturated solutions – more than the max amount of solute at a given temperature; unstable
B. Types of Solutions SATURATED SOLUTION no more solute dissolves UNSATURATED SOLUTION more solute dissolves SUPERSATURATED SOLUTION becomes unstable, crystals form concentration
C. Dissolving Solvation occurs at the surface of the solute solvent particles surround solute particles (+/- attraction) solute particles are pulled into solution
C. Dissolving NaCl dissolving in water
D. Rate of Dissolving Solids dissolve faster... more stirring small particle size (increased surface area) high temperature
D. Rate of Dissolving Gases dissolve faster... no shaking or stirring high pressure low temperature
Ch. 8 Solutions, Acids, & Bases II. Concentration & Solubility
A. Concentration % by Volume usu. liquid in liquid EX: 10% juice = 10mL juice + 90mL water % by Mass usu. solid in liquid EX: 20% NaCl = 20g NaCl + 80g water
A. Concentration Concentrated solution large amount of solute Dilute solution small amount of solute
A. Concentration SATURATED SOLUTION no more solute dissolves UNSATURATED SOLUTION more solute dissolves SUPERSATURATED SOLUTION becomes unstable, crystals form concentration
B. Solubility Solubility maximum grams of solute that will dissolve in 100 g of solvent at a given temperature varies with temperature based on a saturated solution
B. Solubility Solubility Curve shows the dependence of solubility on temperature
B. Solubility Solids are more soluble at... high temperatures. Gases are more soluble at... low temperatures. high pressures (Henry’s Law).
Ch. 8 Solutions, Acids, & Bases III. Particles in Solution “Like Dissolves Like” Electrolytes
A. “Like Dissolves Like” NONPOLAR POLAR Detergents polar “head” with long nonpolar “tail” can dissolve both types
B. Electrolytes Electrolyte Non- Electrolyte solute exists as ions only - + salt - + sugar solute exists as molecules only - + acetic acid Weak Electrolyte solute exists as ions and molecules
B. Electrolytes Dissociation separation of +/- ions when an ionic compound dissolves in water
B. Electrolytes Ionization breaking apart of polar covalent molecules into ions when dissolving in water
Ch. 8 Solutions, Acids, & Bases I. Intro to Acids & Bases Definitions Properties Uses
A. Acids Contain at least one hydrogen atom that can be removed when the acid is dissolved in water. These form hydronium ions, H 3 O +. HCl + H 2 O H 3 O + + Cl –
A. Bases Form hydroxide ions (OH-) in a water solution. NH 3 + H 2 O NH OH -
A. Indicators An organic substance that changes color in an acid or base. Examples: litmus - red/blue phenolphthalein - colorless/pink goldenrod - yellow/red red cabbage juice - pink/green
B. Properties sour taste pH less than 7 corrosive electrolytes turn litmus red react with metals to form H 2 gas bitter taste pH greater than 7 corrosive electrolytes turn litmus blue slippery feel
C. Uses H 3 PO 4 - soft drinks, fertilizer, detergents H 2 SO 4 - fertilizer, car batteries HCl - gastric juice HC 2 H 3 O 2 - vinegar
C. Uses NaOH - lye, drain and oven cleaner Mg(OH) 2 - laxative, antacid NH 3 - cleaners, fertilizer
Ch. 8 Solutions, Acids, & Bases II. Strength of Acids & Bases Strength vs. Concentration Strong vs. Weak pH
A. Strength vs. Concentration Strong and weak – tells how easy the acid or base dissociates in solution. Concentration – The amount of acid or base in a solution. It is possible to have a dilute concentration of a strong acid that would be less harmful than a concentrated weak acid.
A. Strength of Acids & Bases The strength of an acid or base depends on how completely a compound separates into ions when dissolved in water. Ions can carry an electric charge so a strong acid will carry more electricity than weak acid.
B. Strong vs. Weak Strong Acid/Base 100% ions in water strong electrolyte HCl, HNO 3, NaOH, LiOH Weak Acid/Base few ions in water weak electrolyte HC 2 H 3 O 2, NH
B. Strong Acids Acids that ionize almost completely in a solution are strong acids. Ex: HCl, HNO 3, and H 2 SO 4
B. Strong Bases Bases that dissociate completely in a solution are strong bases. Ex: NaOH
C. pH Scale 0 7 INCREASING ACIDITY NEUTRAL INCREASING BASICITY 14 pH (potential of Hydrogen) a measure of the concentration of H+ ions in a solution measured with a pH meter or an indicator with a wide color range (0-14)
C. pH Scale pH of Common Substances
Which of the following "molecular" pictures best represents a concentrated solution of the weak acid HA? ConcepTest AB
Is the following statement TRUE or FALSE? A strong acid has a lower pH than a weak acid. FALSE - Strong/weak refers to amount of ionization whereas pH refers to concentration of H +. ConcepTest
Ch. 8 Solutions, Acids, & Bases III. Neutralization Neutralization Reaction
A. Neutralization Reaction Chemical reaction between an acid and a base. Products are a salt (ionic compound) and water.
ACID + BASE SALT + WATER HCl + NaOH NaCl + H 2 O Neutralization does not always mean pH = 7. = A. Neutralization Reaction
KOH + HNO 3 H 2 O + KNO 3 Acid Base Salt HNO 3 KOH KNO 3 A. Neutralization Reaction