Reactions in Aqueous Solutions AP Chemistry

Water and Electrolytes

4.1 Water, the Common Solvent Many substances ____________________ in water Shape is ____________; bond angle of 104.5o Because oxygen is more electronegative than hydrogen, the water molecule is _______________ dissolve bent polar

bent polar

Hydration-interaction between solute particles and water molecules Example: NaCl dissolved in water

Solubility- the amount of a substance that dissolves in a given volume of solvent at a given temperature

“Like dissolves like” polar dissolves polar nonpolar dissolves nonpolar polar does not dissolve nonpolar nonpolar does not dissolve polar

Alcohols are soluble in water because both are polar

4.2 The Nature of Aqueous Solutions: Strong and Weak Electrolytes Solution: homogeneous mixture Solute: substance dissolved in a liquid to form a solution Solvent: dissolving medium (often water)

Electrical conductivity: ability to conduct electricity; electrolytes do and nonelectrolytes do not

Arrhenius: extent to which a solution can conduct electricity depends directly on the number of ions present 1899

Arrhenius acid: produces H+ in solution Arrhenius base: produces OH- in solution

Strong electrolytes: strong acids, strong bases, soluble salts (ionic compounds) Ionic compounds conduct electricity when molten or dissolved in water

Strong Acids: ionize (dissociate) completely; 100% Strong bases: completely ionize in solution, 100%

Seven strong acids to memorize: HCl HBr HI HNO3 HClO3 HClO4 H2SO4

Eight Strong Bases Group 1: LiOH NaOH KOH RbOH CsOH “Heavy” Group 2: Ca(OH)2 Sr(OH)2 Ba(OH)2

Two Strong Bases to Memorize NaOH KOH These are the most common and are the only ones we will use in the lab

Weak electrolytes: exhibit small degree of ionization, 1%

Weak acids: all acids except the seven strong acids are weak acetic acid (HC2H3O2) Weak bases: all bases except the eight strong bases are weak ammonia (NH3)

molecules do not dissociate even though they are soluble Nonelectrolytes: molecules do not dissociate even though they are soluble covalent compounds Examples: ethanol (C2H3OH) sucrose (C12H22O11)

Dissociation Equations Occur in water (aqueous solution) Be sure and include state symbols Google the compound to find out its most common state @ STP if you are not sure

Examples of Dissociation Equations: HCl (aq) → HNO3 (aq) → NaOH (s) → NH3 (aq) + H2O (l) → H+ (aq) + Cl- (aq) H+ (aq) + NO3 (aq) Na+ (aq) + OH- (aq) NH4+ (aq) + OH- (aq)