chem exam3

K_sp

used to measure the the dissolution of an ionic compound

molar solubility (S)

unit: mol/L

change in S_universe can be used to prove spontaneity when it’s…

greater than 0 (positive)

solubility and pH

• if pH is high, then [OH] is high and equil shifts left

• if pH is low, then [H3O] is high and equil shifts right

hydroxides, sulfides, and carbonates are more soluble in…

acidic water

how does a precipitate form?

when a solution has 2 ionic compounds and one is insoluble

Q and K_sp

• if Q < K_sp, reaction goes right, solution is unsaturated, and more solid can be added

• if Q = K_sp, reaction goes right, solution is saturated, and equil is reached

• if Q > K_sp, reaction goes left, solution is supersaturated, and rhe excess solid precipitates

ligand

neutral molecule/ion that acts as a lewis base with a central ion

complex ion

has a central metal ion bound to 1 or more ligands

when K_f is large, what happens

equil will favor the product and most of the reactant will be used up. in those cases we can use that inital conc as the variable

spontaneous process

can a reaction happen on its own

• in thermodynamics, we consider the direction and extent of the reaction

• in kinetics, we consider the speed of the reaction

• increases with entropy

how can a nonspontaneous process become spontaneous?

by coupling it with a spontaneous process OR getting energy from another source

entropy

• increases with the number of ways (W) to rearrange components

• increases with spontaneity

• unit: J/K

macrostate

overall state of a system defined by given conditions

• remains constant

microstate (W)

number of ways to rearrange components

whats the rank of increasing entropy

solid » liquid » gas

that’s because each state is more disorderly than the last

reversible process

happens at melting/boiling point

• any tiny change can turn it back

sublimation

solid » gas

condensation

gas » liquid

how do you determine entropy from systems graph

• the more levels it has, the more entropy

  • because that means there is more than 1 way to disperse

ranking entropy (S)

• check states

• if states are constant check the complexity

• if complexity is the same, check mols

• if mols are similar on both sides, check molar mass

system entropy vs surrounding entropy

• if S_surr increases by a big amount, S_sys can decrease

• if S_surr is positive, it’s spontaneous under low temps

• if S_sys is positive, it’s spontaneous under high temps

exothermic process

energy disperses into surroundings and entropy increases

endothermic process

energy leaves surroundings and entropy decreases

gibbs free energy (G)

energy available to do useful work

• when it’s spontaneous, change in G is negative

• when it’s nonspontaneous, change in G is positive

• at equilibrium, change in G = 0

change in G vs change in G(degree)

• change in G refers to given conditions

• change in G(degree) refers to standard conditions

change in G

• if Q is very small, then RT*ln(Q) will be a large negative

• if Q is very large, then RT*ln(Q) will be positive

change in G(degree) and K

• if change in G(degree) is negative, then K > 1 (large)

• if change in G(degree) is positive, then K < 1 (small)

• if change in G(degree) = 0, then K = 1

oxidation-reduction reactions

• aka redox reactions

• reactions that create electricity

oxidation

increase in oxidation state (when more electrons are lost in the products)

reduction

decrease in oxidation state (when there’s more gain in electrons in the products)

voltaic cell

a device that uses a spontaneous chemical reaction to make electricity

• forces it through a wire

anode

electron where oxidation happens

• has a negative charge in voltaic cell

• electrons leave from here

cathode

• where reduction happens

• electrons arrive here

salt bridge

• tube filled with electrolytes

• neutralizes charge buildup by letting ions flow

• without it, reaction stops instantly

cell potentional (E_cell)

• unit: volts (V)

• the “push” behind electrons

• if E_cell is positive, reaction is spontaneous

• if E_cell is negative, reaction is nonspontaneous