AOS 1 Flashcards
1
Q
Exothermic Reactions
A
- energy of products is less than energy of reactants = energy is release
- products have lower energy than reactants b/c products are more stable. therefore bonds in products are stronger than reactants so more energy is release when new bonds form in products.
2
Q
endothermic reactions
A
- energy of the products is greater than energy of reactants
- reactants have lower energy than products b/c reactants more stable that products.
this means bonds in - reactants are stronger than in products so more energy is needed to break reactant bonds that is released when new bonds form in products
3
Q
thermochemical equations
A
- show amount of energy absorption or released in a reaction
4
Q
Fuels
Fossil Fuels
A
- coal, natural gas and crude oil
- non-renewable, extraction causes environmental issues, enhanced green house gases.
5
Q
fuels
Biofuels
A
- sourced by organic matter - renewable
- often carbon neutral - CO2 released when burning fuels can be used by plants through photosynthesis
- not always sustainable - fuels produced faster or equal to the rate they are consumer
6
Q
Fuels - biofuels
bioethanol
how is it produced - equation
A
produced by anaerobic fermentation
7
Q
Fuel - Biofuel
Biodiesal
what is it - eq
A
mixture of fatty acid alkyl esters produced by reaction b/w triglycerides
8
Q
Fuel - biofuel
biogas
A
- carbon dioxide and methan
- from organic material unger anaerobic conditions
- reduces the energy gained from fossil fuels
9
Q
complete vs incomplete combustion
A
O2 is limiting reactant
produce CO, CO2 and C(s)
10
Q
Fuel for the body
Fats and Oils
A
- triglycerides
- provides energy and store energy in the body
- 37 Kj per gram
11
Q
fuel for the body
proteins
A
- protein polymer is digested by metabolism = monomers + amino acids
- 16 KJ per gram
12
Q
fuel for the body
carbs
A
polymers of glucose
glycogen storage of carbs in body
higher degree of oxidation
16 KJ per gram
13
Q
cellular respiration
A
14
Q
photosynthesis
A
15
Q
calculations in thermochemistry
A
- Find mass/moles/volume of reactants/products using stoich
- finding energy (released or absorbed in reaction) given AH and moles
- find amount of substance (reacted) needed) given q and AH
- find AH given energy and moles
16
Q
energy efficiency
A
17
Q
specific heat capacity
A
amount of energy needed to raise the temp. of 1g of substance by 1*c.
18
Q
colorimetry
A
- measurement of heat lost or gained in reaction.
- calibration factor = known energy to measure temp. change
19
Q
Calibration factor
A
energy required to raise temp. of a colorimeter and its contents by 1c
20
Q
colorimetry cal.
A
21
Q
redox review
A
- transfer of electrons
- oxidant causes oxidation - reduction
- reductant causes reduction
= oxidation
22
Q
half eq. acidic
A
23
Q
half eq. basic
A
- balance KOH then as OH to both sides to balance H+
- balance ES
24
Q
galvanic cells
A
convert chemical energy into electrical energy.
electrons travel thru from anode (-) to cathode (+)
25
# galvanic cells
diagram - theory
* salt bridge: allows ions to flow, balance charge - complete e- circuit
* anode: cations ions are formed - anions move out of salt bridge
* cathode: cation are consumed so +ions from salt bridge move into cell
26
potential diff.
temp. = 25 c
Pressure = 1 atm
1 M concentration of solution
27
electrochemical cells
primary cells: non-rechargeable - go flat when cell reaches equilibrium. as build up of products around electrodes
28
faraday's law
29
Faraday's law cal.
1. amount of charge generated of current flowing - q=n(e)xF
2. length of tie a cell can run for q=It
3. mass or volume needed/used for certain amount of electricity
4. mass change of electrodes for a certain amount of electricity
30
Fuel Cells
* are spontaneous reactions that convert chemical energy to electrical energy.
* more efficient than combustion engines
* **oxidan**t: O2
* **reductant**: H2 or carbon compound which produces CO2
* fuel moves over anode
31
advantages of fuel cells
* lower emissions of harmful sulfur and nitrogen containing compounds
* low maintenance and running costs
* no direct CO2 emissions from hydrogen fuel cells
* greater efficiency
32
disadvantages of fuel cells
* storage and safety issues associated with highly explosive hydrogen fuel
* expensive to manufacture
* new infrastructure for hydrogen fuel
* hydrogen fuel generally produced bia electrolysis
33
hydrogen fuel cells
Hydrogen fuel cells have less emissions - although production of H causes significant GHG pollutions.
34
fuel cell efficiency
* electrodes are catalytic - currently made from non-renewable materials (Pt)
* electrodes are porous - allow gaseous reactants to diffuse across
* nano materials - increase pores increases surface area = more efficient
* combining with batteries - to store energy produced when its not used
* polymer membrane - electrolytes increases speed of ion movement
* optimal conditions - warmer
35
renewable feedstocks for fuel
| CO2/H2 fuel cells
* CO2 is the oxidising agent instead of O2
* CO2 is renewable source - collected from biomass and removes it from the atmospher
* H2 renewable - electricity used from electrolysis is from renewable sources
* uses fo polymer membrane, carbon nanotubes & Pt as catalyst electrodes
36
renewable feedstocks for fuel
| bioethanol fuel cells
* ethanol as the fuel but uses ethanol from fermentation of glucose from plants
* this may be renewable but material used for catalytic electrodes are not
37
Green chemistry princibles
1. catalysis - electrodes in fuel cells are catalytic. this means it increases efficiency
2. design for energy efficiency.
fuel cells
* more efficient then combustion engines
* heat lost can be used
* catalytic electrodes (Pt)
* nano-material electrodes - smaller & more pores = higher surface area
3. use of renewable feedstocks
* use from biomass - bioethanol, biodiesal and biogas
* electrolysis (renewable electricity) - CO2, H2, bioethanol
38
Un Sustainability development goals
1. zero hunger
* growing crops use land which could be used for food
2. climate action
* fuel cells lower GHG emisions (CO2)
* biofuels: take in CO2 through photosynthesis
* fuel cells: more efficient
3. responsible consumption
*
4. affordable energy
* fuel cells are more expensive
* biofuels are more expensive
5. life on land
* CO2 emmissions
* polutions from fossil fuels - GHG
* extraction of FF = damage to environment
6. sustainable cities
* access feuling stations storage
