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Chemistry exam
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Chemistry exam
Untitled Flashcards
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1
Question
Oxidation vs Reduction
Answer
Oxidation is loss of electrons Reduction is gain of electrons
2
Question
How to balance half equations
Answer
KOHES Key elements Oxygen (use H2O) Hydrogen (Use H+) Electrons State In alkaline conditions Balance H+ by adding OH- to opposite side Convert H+ to H2O
3
Question
Galvanic cell
Answer
A type of electrochemical cell that converts chemical energy to electrical energy
4
Question
Salt bridge/Electrolyte
Answer
Allows the flow of ions to complete the internal circuit and maintain electrical neutrality Anions flow to anode Cations flow to cathode
5
Question
Hydrogen production methods
Answer
Collect biogas from landfill sites and convert to hydrogen by steam reforming Using electrical enegy to split/electrolysis water into oxygen and hydrogen (as long as electrical energy is supplied by renewable energy methods such as solar power plants)
6
Question
Steam reforming equation
Answer
CH4 + H2O(g) --Ni(s)--> CO + 3H2 CO + H2O ----Cu(s)/Fe(s)---> CO2 + H2
7
Question
Material based hydrogen storage
Answer
Can be adsorbed to the surface of some materials (liquid hydrogen) Can be absorbed into the lattice structure of some metals (solid hydrogen)
8
Question
Liquid hydrogen
Answer
Low boiling point (-272 degrees) Lower energy/L than petrol
9
Question
Compressed hydrogen
Answer
High Pressure Lower energy/L than liquid hydrogen
10
Question
Safety considerations for hydrogen storage
Answer
Highly flammable/explosive (keep away from any ignition sources) Odourless and colourless (install hydrogen detectors for leakages) Dissipates quickly (allow for proper ventlation)
11
Question
Advantages of hydrogen fuel cell
Answer
Unlimited supply of electrical energy while fuel is supplied More environmentally friendly as less greenhous gases are emitted (by product of water and heat)
12
Question
Disadvantages of hydrogen fuel cell
Answer
Hydrogen production and storage is difficult and expensive Can be expensive (porous electrodes and catalysts) Unsafe (highly flammable)
13
Question
Microbial fuel cell (MFC)
Answer
Converts organic material (chemical energy) to electrical energy by the action of microorganisms Microorganisms form a film on the anode
14
Question
Advantage of MFC
Answer
Uses low grade waste material like waste water Sustainable waste water treatment and contaminant removal
15
Question
Standard reduction potential
Answer
Tendency of a particular half-cell to gain e- Measured relative to the H2 half cell which has been assigned the value of 0.00V (reference half-cell)
16
Question
Cell voltage
Answer
E reduction - E oxidation
17
Question
Electroplating
Answer
Object being plated is the negative electrode (cathode) The deposition of a thin layer of metal on the surface of another metal
18
Question
Electrolysis
Answer
Negative terminal pushes electrons to the cathode Positive terminal withdraws electrons from the anode using an external power source to force a non-spontaneous reaction to occur
19
Question
Renewable
Answer
Able to be replenished by natural processes in a short period of time
20
Question
Fuel
Answer
Stored chemical energy
21
Question
Renewable fuels
Answer
Biogas Bioethanol Biodiesel
22
Question
Non-renewable
Answer
Coal Crude Oil Natural gas
23
Question
Coal
Answer
Only 35% chemical energy is converted to electrical energy due to undergoing many energy transformations where energy is loss
24
Question
Crude oil
Answer
A mixture of hydrocarbon molecules (mostly alkane)e
25
Question
Natural gas
Answer
Mainly methane (CH4) and some other hydrocarbons (ethane and propane) Gas trapped in coal seams or shale rock undergoes fracking to be collected Converted from gas (chemical energy) to electrical energy via a series of energy transformations (more efficient than coal)
26
Question
Biofuel being carbon neutral
Answer
In theory: same amount of CO2 absorbed from the atmostphere in its formation is the same amount of CO2 released into the atmosphere in its combustion In practice: energy is also required for transporting and farming
27
Question
Bioethanol
Answer
Produced via fermetation of glucose at 35 degrees Catalysed (controlled) by enzymes C6H12O6 (aq) ---> 2CH3CH2OH (aq) + 2CO2 (g)
28
Question
Biogas
Answer
Anaerobic bacteria break down large molecules in organic waste (such as carbohydrates and proteins) to smaller compounds CO2 and CH4
29
Question
Biodiesel
Answer
Mixture of esters - produced by a reaction between vegetable oils or animal fats and alcohol (usually methanol)
30
Question
Main feedstocks for bioethanol
Answer
Sugar cane (high in sucrose) small Wheat (high in starch) medium Forest waste (cellulose) large