Chem- Solutions and Electrochemistry

Water soluble

all salts with (NH_4⁺, NO₃^-) and alkali metal cations, acetate anions, halides (except F and those formed with Ag/Pb/Hg), salts with SO₄^2- (except if formed with Ca/Sr/Ba/Pb)

Insoluble

all metal oxides (except if formed with alkali metals, NH_4⁺, CaO, BaO, SrO), all hydroxides (except if formed with alkali, NH_4⁺, Ca/Sr/Ba), all carbonates/phosphates/sulfides/sulfites (except if formed with alkali and NH_4⁺)

Solubility constant (K_sp)

think of it as a specialized form of K_eq

Common ion effect

solubility of a salt in a solution that already contains one of the ions in that salt is considerably reduced. reduction of molar solubility of the salt. the presence of that ion in solution shifts the dissolution reaction to the left, decreasing its dissociation

Anode

site of OXIDATION

Cathode

site of REDUCTION

Electron flow in electrochemical cells

from anode to cathode

Electron flow in current

cathode to anode

Galvanic cells (voltaic cells)

reactions are spontaneous! E_cell must be positive, free energy change and electromotive force always have opposite signs

Electrolytic cells

nonspontaneous reaction! opposite of galvanic cells.

Concentration cells

spontaneous reaction! specialized galvanic cells

Current in concentration cells

generated as a function of concentration gradient which results in a potential difference between the 2 compartments and drives movement of electrons in the direction that results in equilibrium of the ion gradient. current stops when ionic concentrations are equal.

Anode in galvanic cell

negative because reduction takes place

Anode of electrolytic cell

positive because it attracts anions

Electromotive force

E_cell = E_{red, cathode} - E_{oxid, anode}

Nernst equation

E_cell = E_cell^o - 0.0592 / n log Q