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Chemistry 2017 > Energy And Electrochemistry > Flashcards

Energy And Electrochemistry Flashcards

1
Q

Energy which is stored within every atom, molecule or ion is a sum of the what and what

A

Potential (stored) and kinetic energy

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2
Q

The total energy stored in a substance is called the …?

A

Enthalpy

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3
Q

The change in enthalpy during a chemical reaction is called what and is denoted by what

A

Heat of reaction & Δ

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4
Q

What is meant by ΔH^o

A

Standard enthalpy of reaction is being measured as standard lab conditions have been used

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5
Q

What are the two possible units for enthalpy

A

kJmol-1 or kJ.g-1

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6
Q

How do we measure enthalpy during a reaction

A

Heat Produced - Heat of reactants

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7
Q

What’s an exothermic reaction

A

Chemical reaction which releases heat to the surroundings

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8
Q

In an exothermic reaction should the enthalpy of the products be more or less than the reactants

A

Less, hence ΔH must be negative

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9
Q

What’s an endothermic reaction

A

Chemical reactions which absorb heat from the surroundings

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10
Q

What do endothermic reactions cause the temperature of the surroundings to do

A

Decrease

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11
Q

If a reaction is endothermic must the enthalpy of the products be more or less than that of the reactants

A

More, hence ΔH will be positive

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12
Q

What is an thermochemical equation

A

An equation showing the enthalpy change for the reaction

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13
Q

4 things to remember when writing thermochemical equations

A

Equation must be balanced
State symbols at 25 degrees
Include enthalpy change ΔH
If coefficients are doubled ΔH value must be doubled

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14
Q

Equation for calculating quantity of heat released or absorbed

A

Heat energy released / absorbed = n(specified substance) x molar enthalpy of reaction

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15
Q

Equation for calculating molar enthalpy change for reaction

A

ΔH = (mass of water x ΔTtemperature change x Cpwater/ 4.18) / 1000 x number of moles in a substance

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16
Q

Equation involving rearranged ΔH expression

A

ΔT = (1000 x n x ΔH) / (Cpwater/4.18 x mass of water)

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17
Q

What is a fuel

A

Substance for producing energy via combustion

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18
Q

Two groups of carbon based fuels

A

Biomass (biofuels)

Fossil Fuels

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19
Q

What are biofuels

A

Fuels derived from recently living organisms of their by products

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20
Q

Does burning biofuels result in an increase of carbon dioxide in the earths atmosphere

A

No as its recently been extracted from atmospheric carbon dioxide by growing plants

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21
Q

What are biofuels in relation to carbon

A

Carbon neutral

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22
Q

What is a common biofuel

A

Ethanol is the most widely used biofuel

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23
Q

What are fossil fuels

A

Fuels formed through the anaerobic breakdown of the remains of plant and tiny marine animals which lived millions of years ago

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24
Q

How is energy obtained from fossil fuels

A

Obtained through burning them in air

25
How much of Australia's energy needs are met by fossil fuels
Around 95%
26
3 Advantages of using ethanol as an energy source
Renewable, Emits less harmful air pollutants Domestically produced
27
3 benefits of biodiesel
Renewable Fewer air pollutant emissions overall Domestically produced
28
2 disadvantages of ethanol
Slight decrease in fuel economy | Lack of widespread fuel availability
29
2 disadvantages of biodiesel
Lack of widespread fuel availability | Slightly higher nitric oxide emissions
30
2 advances of coal
Large reserves | Mined at relatively low cost
31
2 advantages of crude oil
Easily extracted | Transported easily
32
3 advantages of natural gas
Easily extracted Transported easily Burns more cleanly than other fossil fuels
33
What are the two main disadvantages of using fossil fuels
They're a major contributor to the enhanced greenhouse effect It's non-renewable
34
Two disadvantages of coal
Produce oxides of nitrogen (can contribute to acid rain and photochemical smog) Produce fine soot particles (can cause respiratory problems)
35
Two disadvantages of crude oil
Produces oxides of nitrogen (can contribute to acid rain and photochemical smog) Produces fine soot particles (can cause respiratory problems)
36
How to convert kJ.mol to kJ.g
kJ.mol divided by molar mass
37
How and what do galvanic cells produce
Electrical energy through spontaneous redox reactions
38
How and what do electrolytic cells produce
Electrical energy from an external source to cause non spontaneous
39
Electrons flow from the ... Reactive to the ... Reactive
Most to Least
40
In oxidation half equations is the e product or reactant
Product
41
In reduction half equations is the e a product or reactant
Reactant
42
AN OIL RIG CAT
Oxidation occurs at the anode | Reduction occurs at the cathode
43
In relation to anodes what direction do electrons flow
Anode to cathode
44
The anions in the salt bridge move towards the
Anode
45
Cations in the salt bridge move towards the
Cathode
46
Can primary / dry cells be recharged
No
47
Can secondary cells be recharged
Yes
48
Electrolytic cells - use ... energy from an ... Source to cause ...
Electrical energy, external sources cause non spontaneous redox reactions
49
In electrolytic cells what is the charge of the anode and cathode
Anode - positive | Cathode - negative
50
What is the reaction at the anode is water is more reactive
2H2O -> O2 + 4H^+ + 4ē
51
What is the reaction at the cathode if water is more reactive
H2O + 2ē -> 2OH^- + H2
52
Overall reaction if water is more reactive at the anode and cathode
6H2O -> 2H2 + O2 + 4H+ + 4OH^-
53
At the cathode molten metals will be '...'
Reduced
54
At the cathode metals in aqueous solution more reactive than what will be what
Aluminium, reduced
55
In aqueous solutions what is most likely to be reduced
Very reactive metals and water
56
At the anode liquids and anions will be what
Oxidised
57
In aqueous solutions an active metal anode will be oxidised in preference to what
Water
58
Electrical efficiency of a fuel cell
70-80%
59
Theoretically how long can fuel cells produce energy for
For as long as the fuel and oxidant are supplied to the electrodes

Chemistry 2017 (5 decks)

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