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Chemistry 2017 > Energy And Electrochemistry > Flashcards

Energy And Electrochemistry Flashcards

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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
Q

How much of Australia’s energy needs are met by fossil fuels

A

Around 95%

26
Q

3 Advantages of using ethanol as an energy source

A

Renewable,
Emits less harmful air pollutants
Domestically produced

27
Q

3 benefits of biodiesel

A

Renewable
Fewer air pollutant emissions overall
Domestically produced

28
Q

2 disadvantages of ethanol

A

Slight decrease in fuel economy

Lack of widespread fuel availability

29
Q

2 disadvantages of biodiesel

A

Lack of widespread fuel availability

Slightly higher nitric oxide emissions

30
Q

2 advances of coal

A

Large reserves

Mined at relatively low cost

31
Q

2 advantages of crude oil

A

Easily extracted

Transported easily

32
Q

3 advantages of natural gas

A

Easily extracted
Transported easily
Burns more cleanly than other fossil fuels

33
Q

What are the two main disadvantages of using fossil fuels

A

They’re a major contributor to the enhanced greenhouse effect

It’s non-renewable

34
Q

Two disadvantages of coal

A

Produce oxides of nitrogen (can contribute to acid rain and photochemical smog)

Produce fine soot particles (can cause respiratory problems)

35
Q

Two disadvantages of crude oil

A

Produces oxides of nitrogen (can contribute to acid rain and photochemical smog)

Produces fine soot particles (can cause respiratory problems)

36
Q

How to convert kJ.mol to kJ.g

A

kJ.mol divided by molar mass

37
Q

How and what do galvanic cells produce

A

Electrical energy through spontaneous redox reactions

38
Q

How and what do electrolytic cells produce

A

Electrical energy from an external source to cause non spontaneous

39
Q

Electrons flow from the … Reactive to the … Reactive

A

Most to Least

40
Q

In oxidation half equations is the e product or reactant

A

Product

41
Q

In reduction half equations is the e a product or reactant

A

Reactant

42
Q

AN OIL RIG CAT

A

Oxidation occurs at the anode

Reduction occurs at the cathode

43
Q

In relation to anodes what direction do electrons flow

A

Anode to cathode

44
Q

The anions in the salt bridge move towards the

A

Anode

45
Q

Cations in the salt bridge move towards the

A

Cathode

46
Q

Can primary / dry cells be recharged

A

No

47
Q

Can secondary cells be recharged

A

Yes

48
Q

Electrolytic cells - use … energy from an … Source to cause …

A

Electrical energy, external sources cause non spontaneous redox reactions

49
Q

In electrolytic cells what is the charge of the anode and cathode

A

Anode - positive

Cathode - negative

50
Q

What is the reaction at the anode is water is more reactive

A

2H2O -> O2 + 4H^+ + 4ē

51
Q

What is the reaction at the cathode if water is more reactive

A

H2O + 2ē -> 2OH^- + H2

52
Q

Overall reaction if water is more reactive at the anode and cathode

A

6H2O -> 2H2 + O2 + 4H+ + 4OH^-

53
Q

At the cathode molten metals will be ‘…’

A

Reduced

54
Q

At the cathode metals in aqueous solution more reactive than what will be what

A

Aluminium, reduced

55
Q

In aqueous solutions what is most likely to be reduced

A

Very reactive metals and water

56
Q

At the anode liquids and anions will be what

A

Oxidised

57
Q

In aqueous solutions an active metal anode will be oxidised in preference to what

A

Water

58
Q

Electrical efficiency of a fuel cell

A

70-80%

59
Q

Theoretically how long can fuel cells produce energy for

A

For as long as the fuel and oxidant are supplied to the electrodes

Chemistry 2017 (5 decks)

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