Jan 2025 final exam - from my paper notes

Question 1

orbital

Answer 1

a wave function describing the probability of finding an electron in a certain place

Question 2

hybrid orbital

Answer 2

multiple orbitals overlapping - constructive/destructive interference

Question 3

geometry for first 5 hybridizations

Answer 3

sp - linear
sp2 - trigonal planar
sp3 - tetrahedral
sp3d - trigonal bipyramidal
sp3d2 - octahedral

Question 4

formal charge formula

Answer 4

FC = #valence electrons - #non-bonding valence electrons - (#bonding electrons)/2

(valence e- - number of electrons IN lone pairs - electrons in bonds/2)

Question 5

how to find optimal lewis dot structure with formal charge?

Answer 5

1. Find the formal charge of each atom in each of the possibl arrangements
2. You want the sum of the absolute values of all the formal charges to be equal to the overall charge of the molecule/ion
3. If more than one arrangement has the same sum of formal charge absolute values, we also want all of them to have a FC of 0 if possible, or as close to 0 as possible, and if none of those are possible the more electronegative elements should have the most negative FC

Question 6

Bonding steps (lewis dot diagram)

Answer 6

1. choose central atom - least electronegative, greatest bonding potential, often highest z, group others around it
2. count total # of valence electrons (all atoms+ionic charge)
3. a sigma bond (1 electron pair) between each atom and the central atom
4. fill in all the lone pairs (octet rule)
5. add a pi bond if central atom’s octet isn’t full
6. any remaining electrons: add as lone pairs on central atom
7. use FC to determine the best option if multiple work

Question 7

bond order for normal bonds (easy)

Answer 7

1 for single,2 for double, etc

Question 8

bond order for structures with resonance

Answer 8

• if there is a sigma bond on each side, start with order 1 (doesn’t matter how many sigma bonds)
• then, look at how many bonds your remaining electron pair is split over. Ex. in ozone, one pair over 2 bonds. in carbonate, 1 pair over 3 bonds. then add: 1/2 or 1/3 respectively, for 1.5 or 1.33 bond order

Question 9

addition polymerization

Answer 9

unsaturated bond broken to form a chain, no by-products, addition reaction

Question 10

addition polymerization mechanism

Answer 10

1. initiation: X2 breaks into 2 halogan radicals (uv light or heat)
2. Propogation: homolytic fission breaking double bond and halogen attaches to the organic molecule, making a radical
   this radical reacts with another alkene to make a longer alkane radical chain, This keeps happening until 2 of these chains react
3. 2 radical chains react, ending the chain reaction and forming a polyalkene (with just a signle bond now) and the halogen on the end

Question 11

condensation polymerisation

Answer 11

bi-functional monomers, condensation reaction, by-product produced

Question 12

Asymetric electrophilic addition mechanism

Answer 12

1. alkene and ex. HCl: Within HCl, H is positive dipole and is attracted to the alkene double bond (exposed pi-bonding electrons). HETEROlytic fission from the bond, hydrogen attaches to a carbon (major product: hydrogen goes to teh carbon with most hydrogens already on there. Chlorine anion formed as well as a carbocation on the 2nd degree carbon, and then they bond too. 2 possible products, one major one minor

Question 13

nitration of benzene: how is nitronium formed?

Answer 13

HNO3 + S2SO4 —-> H2O + NO2+ + HSO4-

Question 14

organic molecules: lower boiling point

Answer 14

• more branched
• shorter chain
• no hydrogen bonding

Question 15

negative enthalpy

Answer 15

exothermic

Question 16

bond enthalpy definition

Answer 16

energy required to break 1 mol of chemical bonds in the gaseous state, endothermic (AVERAGED across the same bonds in similar compounds)

Question 17

reaction enthalpy using bond enthalpy

Answer 17

sum of broken - sum of formed

Question 18

standard enthalpy of combustion definition

Answer 18

energy released when 1 mol of a substance in its standard state is completely burned with oxygen (exothermic)

Question 19

standard enthalpy of formation definition

Answer 19

energy required to make 1 mol of a compound from its constituent elements in their standard states (endothermic)

Question 20

born haber cycle - if you go clockwise, which arrows are facing the opposite direction (which signs do you flip?)

Answer 20

lattice enthalpy and enthalpy of formation

Question 21

lattice enthalpy definition

Answer 21

energy required when 1 mol of a solid ionic compound is formed from its gaseous ions (endothermic)

Question 22

order of born haber cycle things

Answer 22

formation enthalpy of the compound (standard state elements to compound), enthalpy of atomization of the mental (standard state to gas), n*bond enthalpy of the nonmetal (to break the bond so that there is 1 mol of a single gaseous atom), first (and sometimes 2nd) IE of the metal, EA of the nonmetal (now you have 2 gaseous ions), lattice enthalpy

Question 23

how to do calculations w born haber cycle

Answer 23

go clockwise, add them all up (or subtract if arrow is reversed)

Question 24

excess, somewhat limited, limited oxygen: combustion of organic compounds products

Answer 24

CO2+H2O, CO+H2O, C+H2O (always gaseous water)

Question 25

fossil fuels

Answer 25

• highly exothermic and naturally abundant, but bad for environment bc produce greenhouse gasses (absorb IR radiation, hold on to thermal energy)

Question 26

bio fuels

Answer 26

• renewable - burning of biomass (ex. plants) which already make glucose through photosynthesis

Question 27

fuel cells

Answer 27

chemical energy to electrical energy using spontaneous exothermic reactions

Question 28

entropy change of a reaction

Answer 28

sum of standard entropies of products - reactants

Question 29

k (equilibrium constant)

Answer 29

[C]^c[D]^d/[A]^a[B]^b (lowercase are their stoic coeff.

Question 30

K for a spontaneous forward reaction (products favoured @eq)

Answer 30

greater than 1 (and G is less than 0)

Question 31

determining LR

Answer 31

1. find n of each reactant using M and m
2. divide it by its coefficient, lowest number is the LR
3. REMEMBER to use n, not the divided number, in any further calculations

Question 32

atom economy formula

Answer 32

molar mass of desired product / molar mass of all reactants

Question 33

rates definition

Answer 33

change in concentration of reactants or products / time

Question 34

collision theory

Answer 34

for reactions to occur, particles must collide with enough energy to overcome the Ea and with the correct geometry