chem option

calculating the efficiency of an energy transfer

Efficiency = (useful output energy / total input energy) × 100

energy density definition

the energy stored per unit volume

specific energy definition

the energy produced per unit mass

advantages of natural gas (4)

relatively clean

higher specific energy than coal and oil

can be compressed or liquefied for easy transport

does not contribute to acid deposition

disadvantages of natural gas (4)

non-renewable

produces CO2

lower energy density than coal and oil

unevenly distributed around the world

advantages of coal (4)

inexpensive

high specific heat capacity and energy density

can be converted into liquid fuels

distributed throughout the world

disadvantages of coal (4)

mining of coal can cause environmental damage

non-renewable

produces CO2

combustion wit sulfur produces acid deposition

advantages of crude oil/petroleum products (3)

inexpensive

high specific heat capacity and energy density

easily transported

disadvantages of crude oil/petroleum products (4)

non-renewable

produces CO2

drilling for and transportation of crude oil can cause environmental damage

unevenly distributed around the world

fractional distillation separation is based off of:

boiling points

what is assigned an octane number of 100

2,2,4-trimethylpentane

methods of increasing octane number:

catalytic reforming

unevenly distributed around the world

unevenly distributed around the world

cracking

what are aromatisation and isomerisation

the catalytic reforming of straight-chain hydrocarbons with low octane numbers into cyclic or branched chains

what is cracking

breaking long-chain hydrocarbons into short-chain hydrocarbons

what is coal gasification

the process of converting coal into synthetic natural gas (CH4)

write out the production of synthetic natural gas (coal gasification)

C(s) + H2O(g) → CO(g) + H2(g)

CO(g) + 3H2(g) → CH4(g) + H2O(g)

what is coal liquefaction

conversion of coal into liquid hydrocarbons

write out the production of coal liquefaction

nC(s) + (n+1)H2(g) → CnH2n+2(l)

define nuclear fusion

the process of lighter nuclei fusing together to form a heavier nucleus

binding energy per nucleon increases

define nuclear fission

the process of splitting a large unstable nucleus into smaller, more stable nuclei

binding energy per nucleon increases

define the critical mass

the minimum mass of a fuel for the reaction to be self-sustaining

what does a breeder reactor do

produces more fissile material than it consumes

what to do with low level waste

stored until isotopes decay and then disposed in landfill

what to do with intermediate level waste

bury in shallow repositories

what to do with high level waste

vitrification and storage deep underground in a geologically stable area

what is the definition of binding energy

the energy required to disassemble a nucleus into its component nucleons

seperate nucleons have a ___________ mass than the combined nucleus. the difference is known as the _____ __________

greater

mass defect

what units is the result of E=mc^2 in and how to convert to kJ.nucleon^-1

J.nucleus^-1

divide by 1000 and then the mass number

how to convert mass defect from amu to kg

multiply by 1 amu

in order for a gas to absorb IR radiation there must be:

a change in dipole moment of the molecule as the bonds undergo asymmetric stretching or bending

explain the greenhouse effect

short wavelength (UV/Vis) wavelength radiation from the sun reaches the surface of the earth, the earth reradiates this as longer wavelength (IR) which are absorbed by greenhouse gasses and reradiate it back to the surface of the earth

how does ocean acidification occur?

concentration of CO2 in aq and g is in equilibrium

CO2(g) ⇌ CO2(aq)

CO2 reacts with water to form carbonic acid which is a weak acid and dissociates, producing H+ ions

H2CO3(aq) ⇌ H+(aq) + HCO3-(aq)

CO2(aq) + H2O(l) ⇌ H2CO3(aq)

global dimming is caused by

increasing amount of particulates such as oxides of sulfur, ash and soot in the atmosphere that absorb incoming solar radiation

difference between primary and secondary cells

secondary cells are rechargable, the redox reactions that occur at the anode/cathode can be reversed using electricity

advantages and disadvantages of lead acid batteries (+1, -3)

+:simple to manufacture, cheap

-: low energy density, overcharging can lead to the production of hydrogen gas, lead is a toxic metal that can affect the CNS

advantages and disadvantages of nickel-cadmium batteries (+1, -1)

+: charge quickly and have high number of charge/discharge cycles

-: cadmium and nickel can have environmental concerns during disposal

advantages and disadvantages of lithium-ion batteries (+1, -2)

+: high energy density

-: expensive, can explode

lead acid battery: forward and reverse reactions anode/cathode/overall

FORWARD:

Anode: Pb + HSO4- → PbSO4 + H+ + 2e-

Cathode: PbO2 + HSO4- + 3H+ + 2e- → PbSO4 + 2H2O

Overall: Pb + PbO2 + 2H2SO4 → 2PbSO4 + 2H2O

nickel cadmium battery: forward and reverse reactions anode/cathode/overall

FORWARD:

Anode: Cd + 2OH− → Cd(OH)2 + 2e−

Cathode: 2NiO(OH) + 2H2O + 2e− → 2Ni(OH)2 + 2OH−

Overall: Cd + 2NiO(OH) + 2H2O → 2Ni(OH)2 + Cd(OH)2

lithium-ion battery: forward and reverse reactions anode/cathode

FORWARD

Anode: Li (graphite) → Li+ (electrolyte) + e-

Cathode: Li+ (electrolyte) + e- + CoO2 (s) → LiCoO2 (s)

thermodynamic efficiency of a fuel cell equation

ΔG / ΔH × 100 %

how to find Q in the nerst equation

concentration at the anode / concentration at the cathode

what is the equation for photosynthesis

6CO2 + 6H2O → C6H12O6 + 6O2

what part of a molecule is responsible for its ability to absorb visible light

conjugated system

fermentation of glucose reaction

C6H12O6 → 2C2H5OH + 2CO2

why can't vegetable oils be used in diesel engines

they are too viscous

advantages and disadvantages of biofuels (+3, -3)

+: high octane rating, renewable, produces less CO

-: lower specific energy than octane, more volatile and therefore evaporates easily, could otherwise be used for food production

general equation for transesterification of an ester and an alcohol

RCOOR1 + R2OH → R1OH + RCOOR2

proton exchange membrane fuel cell: reactions at anode/cathode

Anode: 2H2 → 4H+ + 4e-

Cathode: O2 + 4H+ + 4e- → 2H2O

alkaline fuel cell: reactions at anode/cathode

Anode: 2H2 + 4OH- → 4H2O + 4e-

Cathode: 2H2O + O2 + 4e- → 4OH-

direct methanol fuel cell: reactions at anode/cathode

Anode: CH3OH + H2O → CO2 + 6H+ + 6e-

Cathode: 3/2O2 + 6H+ + 6e- → 3H2O

microbial fuel cell: reactions at anode/cathode

Anode: CH3COO- + 2H2O → 2CO2 + 7H+ + 8e-

Cathode: 2O2 + 8H+ + 8e- → 4H2O

n type doping is

the addition of a group 15 element, adding an extra electron

p type doping is

the addition of a group 13 element, creating a hole

DSSC iodine oxidation and reduction

Oxidation: 3I− → I3− + 2e−

Reduction: I3− + 2e− → 3I−

a large conjugated system absorbs ________ wavelengths of light

longer

identify a reagent and a catalyst for a transesterification reaction

reagent: methanol/ethanol

catalyst: strong acid/base

ie. HCl/NaOH

why are DSSC so efficient (2)

large surface area

dye converts almost all absorbed photons into electrons

how to go from J to MJ

divide by 1000 then by 1000 again

in concentration cell, the lower concentration will be the

anode

mass defect =c

mass of nucleons - mass of nucleus

the mass of a nucleus can be found by mutiplying the number of _________ by the ________

nucleons amu

E is in

J/nucleus

convert J/nucleus to kj.mol-1

divide by 1000 and multiply by avogadro constant

convert J/nucleus to kJ.nucleon

divide by number of nucleons and then divide by 1000

difference in bonding between UO2 and UF6

UO2 is a crystalline ionic solic (high melting point)

UF6 is a covalent structure - non polar

increasing the T of a metal does what to electrical conductivity

decreases as metal ions vibrate

what does n and p type doping actually do

increased electrical conductivity of the silicon lattice

explain the operation of a DSSC

dye has a conjugated system

dye absorbs a photon and injects an electron into TiO2

electrons transferred to semiconductor

dye takes electron from electrolyte (dye is oxidised)

electron flows through external circuit

types of isotope separation

centrifugation (heavier 238 forced to the outside while lighter 235 stays on the inside)

gaseous diffusion (pass through porous membrane)

how to concentrate U235

convert to UF6 with lower boiling point and then separate based off of molar masses