CHEM 12 FINAL CRUNCH TIME!!!!

electro chemstry, equilibrium, solubility, acid & bases, reaction kinetics... I think thats everything

oxidation

the loss of electrons

H2 + Sn 4+ → 2H+ + Sn 2+ what is being oxidizied?

H2 is being oxidized.

reduction

gain of electrons

H2 + Sn 4+ → 2H+ + Sn 2+ what is being reduced?

Sn 4+ is being reduced.

oxidizing agent

is the ion being reduced, initializes oxidation in the other species

reducing agent

is the ion being oxidized, initializes reduction in the other species.

half reaction

a reaction that occurs in a half-cell of an electrochemical cell that represents either the oxidation or reduction process separately.

redox reaction

a reaction involving the loss and gain of electrons

What is the oxidation number of P in H4P2O7?

+5.

what is the oxygen tip for oxidation numbers?

if the amt of O2 decreases, it is being reduced, if it increases = it is being oxidized.

whats the first rule for O.N’s

Pure elements have an oxidation number of 0.

what is the ON of Na(s)?

0

what is the second rule for O.N’s?

The oxidation number of a monatomic ion is equal to its charge.

what is the O.N for Se-2?

-2

what is the third rule for O.N’s?

The oxidation number of hydrogen is +1 when bonded to non-metals and -1 when bonded to metals (NaH). And with oxygen, it is usually -2 but is -1 with peroxides (Na2O2 or H2O2)

what is the O.N for H in NaH

-1

what is the oxidation number for O2 in H2O2

-1

when an oxidation number decreases.. it is a

reduction rxn

when an oxidation number increases.. it is a

oxidation rxn

What is the balanced equation of MnO4- → MnO2 in acidic conditions?

3e + 4H+ + MnO4- → MnO2 + H2O

what is the balanced equation for MnO4- → MnO2 in basic conditions?

3e + 2H2O + MnO4- → 4OH- + MnO2

balanced equation for Al + Ni+2 → Ni + Al+3 in neutral conditions?

Al + Ni+2 → Ni + Al+3 + e

what would a simple table of reduction half rxns look like using the following =

S2O8-2 +2e → 2SO4-2

Cr+3 + e → Cr+2

I2 +2e → 2I-

2H+ + 2e → H2

S2O8-2 + 2e → 2SO4-2 E= +2.01V

I2 + 2e → 2I- E= 0.54V

2H+ + 2e → H2 E= 0.00V

Cr+3 + e → Cr+2 E= -0.41V

will S2O8-2 +2e and Cr+2 be spontaneous or non spontaneous?

spontaneous

will I2 + 2e and 2H+ + 2e be spontaneous or non spontaneous

non spontaneous

what type of rxn happens at the anode?

Oxidation

the anode is the _____ of electrons

source

what type of rxn happens at the cathode?

reduction

The cathode is the _____ of electrons

taker

Cathode is …. and ……. ions will move towards it

positive ….. cations

Anode is …… and …….. ions will move towards it

negative and anions will move towards it.

the flow of electrons go from

the anode to the cathode.

the cathode will ….. in mass

increase

the anode will ….. in mass

decrease in mass

when equilibrium is reached what will the voltage of the cell be?

0.00V

if a voltage is positive it is…

spontaneous and favors product formation.

if a voltage is negative it is…

nonspontaneous and favors reactant formation.

what does spontaneous mean?

A process that occurs naturally without needing external energy, indicating a tendency to proceed towards product formation. so a rxn without the need of a battery cell. All battery cell reactions are non spontaneous. The reverse rxn though will be spontaneous

voltage of the cell equation

Ecathode - Eanode

what is an electrochemical cell concept in real life

fuel cells and electrolysis

what are the necessary conditions for corrosion to occur

oxygen, water and metal

corrosion is

the oxidation of metals

physical strain in the corrosion process creates

points in metal more likely to oxidize

these points become….. and makes water the….

the anode and electrons will travel through water making the water the cathode

the metal bits and the OH- mix to create..

rust

how can you prevent rusting?

• Coating (painting, greasing, or lubing)

• Sacrificial coating (galvanizing, painting with a more reactive metal)

• Cathodic protection (making the wanted metal the cathode)

• Electric pulses (resetting the oxidation)

define electrolysis

a non-spontaneous redox reaction that is capable of occuring through an external source giving its electrical input

electrolytic cell

the external source essentially LOL

the flow in an electrolytic cell for negative ions is

to the anode

the flow in an electrolytic cell for positive ions is

to the cathode

if there are multiple ions in the solution.. what is used?

negative ion with the most oxidizing potential and the positive ion with the most reduction potential

electroplating

when a metal ion in liquid form is turned to a solid at the cathode (boi.)

metal refining

impure metals are purified through electrolysis to obtain a pure metal at the cathode. The ions of the metal undergo reduction at the anode. (yea man idk)

both reactions happen simantaneoulsy (yes slaughter that spelling) when..

equilibrium is reached between the forward and reverse reactions.

the relation of the concentrations of the reactants and products with the rate of the reactions

before equilibrium [A+B] is higher so the forward rxn rate is faster. Eventually [A+B] slowly starts to decrease as [C+D] starts to increase along with their reaction rates until equilibrium is met

equilibrium in closed systems have

-constant rates

-constant concentrations

-constant macroscopic properties.

what is enthalpy

heat energy change of a rxn.

if overall H<0 it is..

exothermic

if overall H>0 it is..

endothermic

entropy

amt of “randomness”

enthalpy and entropy favour the products if

rxn is spontaneous at all time and ΔH < 0 (endothermic) and ΔS > 0

enthalpy and entropy favour reactants if

rxn is nonspontaneous at all time and ΔH > 0 (endothermic) and ΔS < 0 both

entropy favours the products, enthalpy favourites the reactants/ vice versa. *

The system has a lower energy state and higher disorder and ΔH < 0 (endothermic) and ΔS > 0 both favor reactants.

• High T → entropy (ΔS) wins

• Low T → enthalpy (ΔH) wins

if an equilibrium is shifted to the left.. what side is favoured

reactants

if an equilibrium is shifted to the right.. what side is favoured

products

if a reaction is exothermic and heat is increased…

it shifts to the reactants

if a rxn is endothermic and heat is increased it…

shifts to the products

if the concentration of the reactants is increased, equilibrium shifts

to products

if the concentration of products is increased, equilibrium shifts

to reactants

the less volume, the more pressure, equilibrium will shift to the side with

fewer molecules

the more volume, the less pressure, equilibrium will shift to the side with

greater molecules

what is the keq expression using : A+B→ C+D

[C]^c [D]^d / [A]^a [B]^b

what is the keq expression for : N2(g) + 3H2(g) → 2NH3(g)

[NH3]²/[N2][H2]³

what is the keq expression for : CaCO3(s) → CaO(s) + CO2(g)

[CO2(g)]

if the keq>1, it will go towards

the products

if keq<1 it will go

to the reactants

if keq=1 it will go

nowhere, it is in equilibrium

what changes the keq value?

temperature

for exothermic reactions and a temperature increase.. it will move to the

reactants

for endothermic reactions and a temperature increase.. it will move to the

products

if the temperature is raised in an exothermic rxn, what happens to the keq value?

decreases

if the temperature increases in an endothermic rxn, what happens to the keq value

increases

solubility units

g/100g, g/L, mol/L

how do i find ΔS

Sf (amt of molecules) - Si

describe the equilibrium that exists in a saturated aqueous solution

the forward rxn is the dissolving rxn

the reverse rxn is the crystallizing rxn

what is the concentration of Na in a 6.0M solution of Na3PO4? Na3PO4 → 3Na+ + PO4-3

18.0M

is a metal+nonmetal solution ionic or molecular?

ionic

is a polyatomic metal + polyatomic nonmetal ionic or molecular?

ionic

is a polyatomic metal + nonmetal ionic or molecular?

ionic

is a metal + polyatomic nonmetal ionic or molecular?

ionic

what is the common ion effect?

when you add an ion that is already in the equation to increase its concentration and shift the equilibrium to reduce that ion

the common ion effect creates

less dissociation

what would u add in this solution to decrease the solubility of AgCl : AgCl(s) → Ag+ + Cl-

NaCl to increase the Cl- and shift the equilibrium left

write out the ksp expression for AB2→ A+2 + 2B-

[A][B]²

write out the ksp for CaF2→Ca+2 + 2F-

[Ca][F-]²

when do you calculate for trial Ion Product?

• Will a precipitate form?”

• “Is the solution saturated?”

• given ion concentrations

when do you calculate for ksp?

• “Ksp = …” (given in a table)

• “Find the Ksp”

• “solution at equilibrium”

when calculating the ksp for Ca + 2F- what can you simplify it to

4s³

if Q>ksp

a ppt forms

if Q=Ksp

at equilibrium