Unit 3 AOS 1 Flashcards
1
Q
Define a gas
A
a state of matter whereby the individual particles are widely spaced apart and are moving independently of another.
2
Q
Are there intermolecular forces between gases?
A
Not in general
3
Q
Why can gases be easily compressed?
A
This is due to low density of the gas, and as they are widely spaced
4
Q
What is pressure?
A
Force of a gas on the walls of the vessel per unit surface area
5
Q
Pressure equation
A
Pressure = force/area
6
Q
Standard unit for pressure
A
Pascal (Pa)
7
Q
How many kPa is in one atmosphere?
A
There are 101.3kPa (101 325 Pa) in one atm
8
Q
How many mmHg is in one atmosphere?
A
There are 760mmHg in one atm
9
Q
How many kPa is in one bar?
A
100kPa
10
Q
Ideal gas equation
A
PV=nRT
11
Q
Gas equation using m/M instead of mol
A
PV=mRT/M
12
Q
Using gas equation to find m
A
m=PVM/RT
13
Q
Charles’ Law
A
V/T is a constant value and V1/T2=V2/T2
14
Q
Boyle’s Law
A
PV=C, where C is a constant value and P1V1=P2V2
15
Q
Charles’ Law and Boyle’s Law is combined to give the equation
A
P1V1/T1=P2V2/T2
16
Q
What is the value of R + what are the units for R
A
8.31JK-1mol-1
17
Q
Formula to find mole using volume and molar volume
A
n=V/Vm
18
Q
What are STP conditions (pressure, temp and molar volume)?
A
pressure = 100kPa, temp = 0ºC and molar volume= 22.7Lmol-1
19
Q
What are SLC conditions (pressure, temp and molar volume)?
A
pressure = 100kPa, temp = 25ºC, molar volume = 24.8Lmol-1
20
Q
Chemical energy (enthalpy) definition
A
energy contained within the various electric forces within and between species.
21
Q
Symbol for enthalpy
A
H
22
Q
Change in enthalpy definition
A
the amount of energy released or absorbed in a chemical reaction. Denoted by the symbol delta H.
23
Q
What unit is enthalpy measured in?
A
kJ mol-1
24
Q
Two main categories of energy
A
kinetic energy, potential energy
25
Examples of kinetic energy
heat, sound, light, chemical and mechanical energy.
26
Examples of potential energy
gravitational, electrical, nuclear, elastic, magnetic, and chemical energy.
27
Activation energy definition
the minimum amount of energy required to commence a reaction
28
If the delta H is positive, then the reaction is (endothermic or exothermic):
endothermic
29
If the delta H is negative, then the reaction is (endothermic or exothermic):
exothermic
30
Exothermic equations definition
describes a chemical reaction in which energy is released to the surroundings.
31
Define a fuel
a substance that can be reacted with other substances, leading to the release of energy that can be harnessed for a specific purpose i.e. a chemical that has stored (potential) energy.
32
Renewable energy resource definition
can be replenished and replaced by natural processes within a relatively short period of time; consumed slower or equal rate than the rate at which it is produced
33
Renewable energy sources are…
sustainable
34
Biofuels are produced from…
living or recently deceased plants (or animals)
35
What is a secondary fuel + example
a fuel that is produced from another energy source. E.g. electricity.
36
Define carbon neutral
no net production/release of CO2 into atmosphere
37
How many kg is 1 tonne
1 tonne = 1000kg
38
Petroleum is…
viscous
39
How is coal produced
Coal is created from wood and other plants breaking down into organic matter. As it decomposes, the Carbon content increases and water is lost. Over time, the coal becomes peat, followed by brown coal and eventually black coal. As the coal develops further due to increased heat, time and pressure, the fuel quality also increases.
40
Dangers of fossil fuels (4)
global warming, destruction of habitats, contamination of water, oil spills
41
How coal seam gas is extracted
drill into ground, pump water to surface to cause reduction in pressure to allow methane to desorb from coal, coal is brought to surface
42
Examples of fossil fuels
coal, petroleum, natural gas
43
An explosion is endothermic/exothermic
exothermic
44
Crude oil can be broken down into (6)
liquified petroleum gas, petrol, kerosene, diesel, fuel oil, hydrocarbons
45
Least to most energy content (4)
wood, black coal, petrol, natural gas
46
An explosion is endothermic/exothermic
exothermic
47
Comparing Biodiesel to petrodiesel (4)
1) biodiesel is more viscous, 2) petrodiesel produces more CO2/SO2/particulate emission but biodiesel produces more NOx, 3) biodiesel more environmentally friendly than petrol, 4) non toxic,
48
Biodiesel definition
A fuel produced from vegetable oil or animal fats and combined with an alcohol, usually methanol.
49
Transesterification definition
The reaction between an ester of one alcohol and a second alcohol to form an ester of the second alcohol and an alcohol from the original ester
50
Heat of vaporisation of water value
40.7kJ mol-1
51
Heat of fusion of water value
6.02 kJ mol–1
52
Unit for specific heat capacity
J/g/degree celsius
53
Specific heat capacity of water value
4.18 J/g/degree celsius
54
Efficiency of energy equation
energy in desired form/total energy
55
Delta H equation
Delta H = H products - H reactants
56
What is the term for when the delta H value is 0?
thermo-neutral
57
How to find energy released/mol
E released/mol = deltaH/mol of element given
58
Density formula
d=m/V
59
Are fossil fuels carbon neutral
no
60
What is a non-renewable resource that is carbon neutral
nuclear fission
61
What are types of biofuels (4)
biomass, liquid fuels, biogas, wind turbines e.t.c.
62
Example of biomass
wood
63
How is biogas produced (specifically methane)?
methane is produced by bacteria breaking natural material
64
Is methane or carbon dioxide more potent?
methane is more potent and difficult to remove from atmosphere
65
How is bioethanol produced?
produced be fermentation of glucose molecules - biomass crops
66
Does ethanol or petrol have a lower density?
ethanol
67
Properties of ethanol (3)
clean burn, hygroscopic, corrosive
68
How many mL in cm^3
1mL = 1cm3
69
How many cm^3 in 1L
1L = 1000cm^3
70
How many K for 1 degree C
1 degree C - 273K
71
Define redox reaction
reactions that involve the transfer of one or more electrons between chemical species
72
Reduction
reaction involving the gain of electrons
73
Oxidation
reaction involving the loss of electrons
74
Galvanic cell definition
a primary cell that uses a redox reaction to convert chemical energy to electrical energy
75
Primary cell definition
a cell that converts chemical energy to electrical energy and cannot be recharged.
76
Electrochemical series definition
a list of half cells in order of highest to lowest reducing strength.
77
Voltmeter definition
a piece of equipment that measures the voltage through a circuit.
78
Voltage definition
the potential difference between two half cells
79
Reductant
chemical species that causes reduction but is itself oxidised.
80
Oxidant
the chemical species that causes oxidation but is itself reduced.
81
Standard electrode potential definition
the potential of a half cell to gain electrons.
82
In a galvanic cell, electrons go from the …. to the …
anode to the cathode
83
In a galvanic cell, the cathode end is… (oxidised or reduced):
reduced
84
In a galvanic cell, the anode end is... (oxidised or reduced):
oxidised
85
What is a dry cell?
an electrochemical cell in which the electrolyte is a paste, rather than a liquid
86
Rules for oxidation numbers
group 1 = +1, group 2 = +2, F = -1, H = -1 unless in a metal in which it is +1, O = -2 unless in peroxide in which it is -1 and with F in which it is +2
87
For oxidation, what happens to oxidation number?
It increases
88
For reduction, what happens to oxidation number
it decreases
89
Where is the strongest oxidant on the electrochemical series?
top left hand corner
90
When asked to find redox reaction in acidic/basic conditions…
acidic is normal using H to balance, and basic means you put OH as products and H2O as reactants.
91
In acidic conditions, what is produced by anode and used by cathode
H+ produced by anode, used by cathode
92
What half cells are in the Leclanche cell?
zinc/carbon
93
What half cells are in Daniell cell?
zinc and copper
94
Types of primary cells (3)
dry cell, button cell, alkaline cell
95
Types of secondary cells (2)
lithium ion, lead-acid
96
What is involved in alkaline fuel cell?
hydrogen and oxygen
97
Direct methanol fuel cell
pure methanol, easier to transport than hydrogen, hold charge better used for laptops/phones
98
Advantages of fuel cells (3)
higher efficiency, portable, low pollution
99
Disadvantages of fuel cells (1)
expensive
100
Difference between galvanic cells and fuel cells (6)
fuel cells require enjoying supply of reactants while galvanic is definitive supply, fuel cell uses fuel while galvanic uses electrodes and ions, electrodes are separated but contained in same vessel for fuel but separate vessels for galvanic, electrodes are porous and contain catalysts for fuel but take part in reaction for galvanic, products are removed for fuel but products build up for galvanic primary, no salt bridge for fuel but there is for wet galvanic but not for dry cell,
101
What are thermal power plants
devices that generate electricity and heat generated from a chemical (or nuclear) reaction. Main method for electricity.
102
Are thermal power plants efficient
no, they are very inefficient
103
Fuel cells compared to thermal power plants (5)
fuel cells are more efficient than combustion engines and thermal power plants, they lead to a lower production of greenhouse gases as they are more efficient - need less fuel to generate same amount of energy and therefore emit less CO2 per amount of energy generated, operate with minimal noise due to presence of fewer moving parts
104
What are button cells?
Small, long-life cells used in devices such as calculators, hearing aids, pacemakers, cameras and watches
105
Types of fuel cells (6)
AFC, PEMFC, PAFC, MCFC, SOFC, DMFC,
106
AFC stands for
alkaline fuel cell
107
PEMFC stands for
proton exchange membrane fuel cell
108
PAFC
phosphoric acid fuel cell
109
MCFC
molten carbonate fuel cell
110
SOFC
solid oxide fuel cell
111
DMFC
direct methanol fuel cell
112
Faraday’s constant
96500C mol-1
113
Rate of transfer of change
change transferred in C/time taken in s
114
1 ampere = …
1 ampere = 1Cs-1
115
What happens during recharging?
during recharge anode and cathode swap, polarity doesn’t change, electron flow from anode to cathode
116
Discharging cell means...
not charging aka normal
117
Efficiency of fuel cells vs fossil fuels
40-60% for fuel cells and 30-35% for fossil fuels
118
Purpose of salt bridge
the salt bridge completes the electric circuit through providing a pathway for the movement of ions to balance charges that are being created or destroyed in the half cells. Cations from the salt bridge migrate towards the half cell that is losing positive charge and the anions migrate to the half cell that is developing a positive charge. In this manner, no charge accumulation occurs.
119
In what conditions are gases "normal"
At high temperatures and low pressure
