Gases and Stoichometry Flashcards
(145 cards)
1
Q
What is stoichiometry sometimes referred to as?
A
“reacting qualities” or “reacting amounts”
2
Q
What are the steps in any calculations question?
A
- Write out and balance the equation
- Determine moles of known
- Identify mole ration
3
Q
What is the limiting reagant?
A
The reagant that will run out first
4
Q
Equations to calculate moles
A
n=CV
n=V/Vm
n=m/Mr
n=PV/RT
5
Q
What are properties of ideal gases?
A
- Particles are in constant and random motion
- Particles are very far apart
- The volume of particles is negligible compared with the volume that the gas occupies
- There are negligible attractive or repulsive forces between particles
6
Q
What is an ‘ideal gas’?
A
an ideal gas is a simplified model that helps us understand how gases should behave under normal conditions — even though no gas is truly “ideal” in the real world.
7
Q
100kPa=
A
750mmHg=0.987atm
8
Q
750mmHg=
A
100kPa=0.987atm
9
Q
0.987atm=
A
100kPa=750mmHg
10
Q
What is the equation to convert from mmHg to kPa?
A
pressure/750 x 100
11
Q
What is the equation to convert from atm to kPa?
A
pressure/0.987 x 100
12
Q
What is the equation to convert from mmHg to atm?
A
pressue/750 x 0.987
13
Q
What is Boyle’s Law and its equation?
A
Pressure and volume are inversely related — when one goes up, the other goes down (as long as temperature and gas amount stay the same).
p1V1 = p2V2
14
Q
What is Charle’s Law and what is the equation?
A
Volume and temperature are directly related — when one goes up, the other goes up too (as long as pressure and amount of gas stay the same).
V1/T1 = V2/T2
15
Q
What is the difference between Boyle’s and Charle’s Law?
A
Boyle’s Law = relationship between pressure and volume
Charles’s Law = relationship between temperature and volume
16
Q
Besides the main equation, what is the other equation for Boyle’s Law?
A
PV = k
17
Q
Besides the main equation, what is the other equation for Charles’s Law?
A
V=kT
18
Q
0 degrees celsius = (in kelvins)
A
273K
19
Q
What does STP stand for and what are they?
A
Standard Temperature and Pressure
Standard temperature is 0 degrees celsius or 273K and standard pressure is 100kPa
20
Q
What does SLC stand for and what are they?
A
Standard Laboratory Conditions
MORE COMMON
Temperature of 25 degrees celsius or 298K
Pressure of 100.0kPa
21
Q
Explain molar volume and avogrado’s hypothesis
A
It has been found experimentally that 1 mole of any gas at SLC occupies a volume of 24.8L
It means that if two gases have the same temperature, pressure and volume, they must occupy the same number of moles
22
Q
Molar Volume equation
A
V=n x Vm
n=V/Vm
Vm=n x Vm
23
Q
What does the Ideal Gas Equation actually mean?
A
The behavior of an ideal gas (a gas that perfectly follows the gas laws) depends on its pressure, volume, temperature, and amount (moles).
24
Q
What is the general gas equation/ideal gas equation/universal gas equation?
A
PV=nRT
25
How do you know when to use the Ideal Gas Equation?
Used when not at SLC
26
In the Ideal Gas Equation, what unit is n?
moles
27
In the Ideal Gas Equation, what unit is P?
kPa
28
In the Ideal Gas Equation, what unit is V?
L
29
In the Ideal Gas Equation, what unit is R?
8.31JK-1mol-1
30
In the Ideal Gas Equation, what unit is T?
K
31
What does R represent?
The universal gas constant and is 8.21JK-1mol-1 when P is measured in kPa, V is measured in L, T is measured in K and n is measured in moles
32
What is the first step in ALL stoichiometry questions?
BALANCED EQUATION
33
Define a Fuel
A fuel is a substance that releases a usable amount of energy when combusted.
34
What two main categories can we class fuels into and provide some examples?
-Fossil Fuels (sourced from the earth) = coal, crude oil, natural gas
-Biofuels (sourced from organic matter) = biogas, bioethanol, biodiesel
35
What does 'combusted' mean?
Burnt
36
What is a greenhouse gas?
A greenhouse gas is a gas in the atmosphere that traps heat from the sun and helps keep the Earth warm. These gases allow sunlight to enter but prevent some of the heat from escaping back into space, creating a "greenhouse effect."
37
Provide some examples of some greenhouse gases
Carbon dioxide, methane, water vapour, nitrous oxide
38
Explain the Natural Greenhouse Effect
Naturally occurring molecules such as CO2, CH4 and water vapor (H20) are greenhouse gases which can trap infra-red radiation that otherwise would be radiated from the earth into space. This increases the temperature of the lower atmosphere which would average 19 degrees celsius without greenhouse gases!
39
Explain the Enhanced Greenhouse Effect
Industrial activity and other human activities can cause the release of more greenhouse gases into the atmosphere. These 'enhance' the greenhouse effect, further increasing the atmospheric temperature. The major greenhouse gases produced as a result of human activity are CO2, CH4, H20 and N20
40
What is the difference between the natural and the enhanced greenhouse gas effect
The natural greenhouse effect and the enhanced greenhouse effect both involve the trapping of heat in the Earth's atmosphere, but the enhanced greenhouse effect is caused by human activities and has more significant impacts.
41
What does combustion of a fuel mean?
Refers to its reaction with oxygen
42
What are the products in COMPLETE COMBUSTION?
Carbon dioxide and water
43
What are the products in INCOMPLETE COMBUSTION?
Carbon monoxide and water
OR
Carbon and water
44
What are the problems caused by the enhanced greenhouse effect?
The enhanced greenhouse effect contributes to a warmer climate, leading to sea level rise, more extreme weather events, loss of biodiversity, and negative effects on agriculture and human health.
45
A positive heat of combustion (exothermic) will produce a ..... enthalpy change
NEGATIVE
46
What two parts does a thermochemical equation contain?
The equation itself and a description of the molar enthalpy change
47
Show the ionic equation of AgCl
Ag+ + Cl- > AgCl
48
What does Acid-Base reactions actually mean?
Acid = proton donor, Base = proton acceptor
49
If water acts as a base and ACCEPTS the proton, what is it now?
H3O+
CONJUGATE ACID
50
When a base accepts a proton (H⁺), the result is called the...
Conjugate acid
51
When an acid donates a proton (H⁺), the resulting species is called the...
Conjugate base
52
What is a neutral solution?
Solution with a pH of 7
53
What is a neutralisation reaction and the formula?
A neutralization reaction is a specific type of acid-base reaction in which the acid and base react to form water (H₂O) and a salt
Base + Acid > Water + Salt
(Metal) Carbonate + Acid > Salt + Water + Carbon Dioxide
54
Neutralisation reactions =
WATER PRODUCED
55
Base + Acid >
Salt + Water
56
Carbonate + Acid >
Salt + Water + Carbon Dioxide
57
Water + Acid >
Hydronium + Anion
58
Water + Alkali >
Hydroxide + Cation
59
Hydronium formula
H30+
60
Metal + Oxygen >
Metal Oxide
61
Metal + Non-Metal >
Salt
62
Metal + Acid >
Salt + Hydrogen
63
Metal + Water >
Metal Hydroxide + Hydrogen
64
Metal + Steam >
Metal Oxide + Hydrogen
65
What is general formula and what needs to occur for a displacement reaction?
A metal must be more reactive than the metal it is displacing in order for the reaction to take place.
Metal 1 + Metal 2 Compound > Metal 2 + Metal 1 Compound
66
What is gravimetric analysis?
A technique through which the amount of an analyte can be determined through the measurement of mass before and/or after a physical or chemical change.
67
In gravimetric analysis (and when a precipitation reaction is involved), what do we do in order to ensure the precipitate is pure?
We rinse it with dissolved water to remove soluble ions and 'dry to constant mass' to ensure that all the water has been removed.
68
What is the analyte?
The ion or solution being analysed
69
What is the precipitate?
A solid that is formed in a reaction between two dissolved substances or gases
70
What is residue?
The solid remaining in the filter paper during filtration
71
What does filtrate mean?
The liquid that passes through the filter paper during filtration
72
What does dry to constant mass mean?
A process in which a solid is weighed, dried, and reweighed until the mass no longer changes. This ensures that all of the excess water has been completely removed.
73
Is the analyte the limiting or excess reagant?
LIMITING
74
What actually is gravimetric analysis?
Gravimetric analysis is when you turn something dissolved into a solid, weigh it, and use that to figure out how much of it was in the solution.
75
Quantitative vs Qualitative Data
Quantitative = data which provides a numerical value, such as mass, volume, temperature, voltage or elapsed time
Qualitative = non-numerical data collected based on observations taken during the experiment, such as bubbling, color change etc
76
What is a systematic error?
An error in measurement by the same amount/proportion in the same direction every time. (a consistent mistake that happens in the same direction every time you do an experiment.)
77
Example/Method of Gravimetric Analyis in finding how much chloride is in a solution
Want to find out how much chloride (Cl⁻) is in a solution.
You add silver nitrate (AgNO₃).
It reacts with the chloride to form silver chloride (AgCl), which is a white solid.
You filter and weigh the AgCl.
From the mass of AgCl, you can calculate how much chloride was in your original sample.
78
What is a random error?
An error in measurement that differs in amount/proportion each time the experiment is conducted. (a small, unpredictable change that happens when you do an experiment — just from natural variation or chance)
79
What is a personal error?
a mistake made by the person doing the experiment — it's basically human error.
80
What is a parralax error?
A parallax error is a reading mistake that happens when you look at a scale from the wrong angle.
81
How to manage systematic errors?
Best managed by calibrating equipment so that all measurements reflect the true value being measured
82
How to manage random errors?
Repeat experiment multiple times and take the average (mean) of your results
83
What does accuracy refer to?
Whether measurements are close to the true value being measured.
84
What does precision refer to?
Whether measurements are close to their mean value, whether or not this is the true value. (CONCORDANT RESULTS)
85
Explain the collision theory
For a chemical reaction to occur, the reactant particles must collide.
There must be correct orientation and sufficient energy to disrupt the bonds in their molecules.
Molecules moving too slowly bounce off each other because their outer shell electrons repel. If the colliding particles have overcome the repulsion and have sufficient energy, this forms new bonds = SUCCESSFUL COLLISION
86
Define Activation Energy
The minimum amount of energy required for a reaction to take place
87
For a reaction to occur, the particles must have energy.....than the activation energy
equal to or greater
88
increasing number of particles with sufficient energy >
increases rate of reaction
89
What are the two parts in a Maxwell-Boltzman Distribution?
Large amount of particles that don't have enough energy for successful collisions and then small number of particles that have high enough energy to react/have a successful collision.
90
What is Rate of Reaction and what are the units?
It is the speed at which a reaction occurs.
Units are the change in concentration of a reactant or product per time.
M/s or Ms-1
M= concentration
s= seconds
91
What does the gradient in a rate of reaction graph tell you?
The rate of change/the rate at which a reactant is being used or a product being used. high gradient=fast reaction, lower gradient=slower reaction
92
What are the five factors effecting rate of reactions?
-Changing the surface area of solid reactants
-Changing the temperature of the reactants
-Changing the concentration of a solution
-Changing pressure of reactant gases
-Using a catalyst
93
INCREASING THE FREQUENCY OF SUCCESSFUL COLLISIONS BETWEEN PARTICLES >>>
INCREASE RATE OF REACTION :)
94
Explain impact of surface area on rate of reaction
increased surface area > more particles are exposed and available to collide > increased frequency of collisions > increased successful collisions > increase rate of reaction
95
Explain impact of concentration on rate of reaction
increased concentration > more particles in the same space > more collisions > frequency of successful collisions increased > increases rate of reaction
96
Explain impact of pressure on rate of reaction
increased pressure > particles more crowded together b/c decreased volume > more collisions > frequency of successful collisions increases > rate of reaction increases
97
Explain impact of temperature on rate of reaction
increased temperature > increase in heat energy > increases the proportion of particles that have energy equal to or greater than the activation energy > increases collisions > increases frequency of successful collisions > rate of reaction increases
98
What does a catalyst do and explain impact of catalysts on rate of reaction
Catalysts lower activation energy.
addition of catalyst > increases proportion of particles that have energy equal to or greater than the activation energy > increases frequency of successful collisions > increases reaction rate
99
How do catalysts work?
The particles on the catalyst surface disrupt bonds within the molecule and lower the activation energy for a reaction.
The overall reaction is unchanged, but the chemical pathways is altered.
100
Classify the five factors affecting RoR whether 1. they increase collision frequency or 2. they increase the proportion of collisions with energy equal to or greater than the activation energy
1. Increased SA, Increased C, Increased P
2. Increased temp, Presence of a catalyst
101
Define reliability and give an example
An experiment can be repeated several times with consistent results.
e.g multiple ppl performed the same experiment multiple times and obtain the following results 100.2, 100.1, 100.2. These consistent results indicate that the method for measuring the boiling point is reliable.
102
Define reproducibility and give an example
A measurement is reproducible if the investigation is repeated by another person, or by using different equipment or techniques, and the same results are obtained.
e.g the C of NaCl solution using a titration method. you perform the titration and find the c to be 0.5M. Another chemist in a different lab repeats the experiment using a different titration set up and obtains the same concentration of 0.5M
103
Equation to calculate rate
Rate = change in quantity/change in time
104
Define a closed system (example may help)
A closed system lets energy move but keeps all matter trapped inside.
(
e.g A sealed container where a reaction happens — no gas or liquid can escape or enter,
but it can still get hotter or cooler)
105
What is a dynamic equillibrium?
A dynamic equilibrium is when a reversible reaction happens in both directions at the same rate, so the amounts of reactants and products stay constant.
106
What does 'forward' and 'reverse' reaction mean?
forward = making products
reverse = turning products back into reactants
107
What is the concentration at dynamic equillibrium?
The concentration of the products and the reactants will remain constant, not necessarily equal
108
Outline one sentence explanation of how a dynamic equilibrium works
AS THE REACTANTS OF THE FORWARD REACTION ARE BEING USED UP, THE PRODUCTS OF THE REVERSE REACTION ARE BEING PRODUCED
109
Give an example of a dynamic equilibrium
Nitrogen and hydrogen react to form ammonia (the forward reaction), ammonia molecules are breaking back down to give nitrogen and hydrogen (the reverse reaction) SIMULTANEOUSLY
110
What is Le Chatelier's Principle?
Le Chatelier’s Principle says that if you change something in a system at equilibrium, the system will try to undo that change to get back to balance.
111
According to Le Chatelier's Principle, if you heat it up, it wants to....
cool down
112
According to Le Chatelier's Principle, if you increase pressure, it wants to....
release pressure
113
According to Le Chatelier's Principle, if you add more concentration, it will...
decrease concentration
114
According to Le Chatelier's Principle, if you add a catalyst, it will....
NOT SHIFT THE EQUILIBRIUM'S POSITION, IT WILL INCREASE BOTH THE FORWARD AND REVERSE REACTION RATE
115
What does positive enthaply change mean (deltaH = +ve)?
Positive ΔH (+ΔH) means that heat is absorbed during the reaction. This is called endothermic because the system takes in heat from its surroundings.
116
What does negative enthaply change mean (deltaH = -ve)?
Negative ΔH (-ΔH) means that heat is released during the reaction. This is called exothermic because the system releases heat to its surroundings.
117
What does deltaH mean?
Change in enthalpy which is a measure of the heat energy in a reaction.
118
When there is an increase in temperature and positive enthalpy change, which reaction is favoured, which way does the equilibrium shift and why?
Forward reaction
Right
Absorbs extra heat = cools down
119
If the forward reaction is endothermic (absorbs heat) →
The system will favour the forward reaction to absorb heat and cool down.
120
If the reverse reaction is endothermic →
The system will favour the reverse reaction instead.
121
When there is an increase in temperature and negative enthalpy change, which reaction is favoured, which way does the equilibrium shift and why?
Endothermic reaction = reverse reaction
Left
Opposes added heat by going backward
122
When there is a decrease in temperature and positive enthalpy change, which reaction is favoured, which way does the equilibrium shift and why?
Exothermic = reverse reaction
Left
System gives off heat to warm back up
123
When there is a decrease in temperature and negative enthalpy change, which reaction is favoured, which way does the equilibrium shift and why?
Exothermic = forward reaction
Right
Releases heat to warm up the system
124
If there is an 🔥 Increase temp, what reaction is favoured and why?
Endothermic reaction because it absorbs heat to cool system down
125
If there is an ❄️ Decrease temp, what reaction is favoured and why?
Exothermic reaction because it releases heat to warm it back up
126
If it is a positive enthalpy change, what type of reaction is it and why?
Endothermic Reaction because it absorbs heat
127
If it is a negative enthalpy change, what type of reaction is it and why?
Exothermic because the reaction releases heat
128
Le Chatelier’s Principle for concentration
If you add more of something, the system will try to use it up.
If you take something away, the system will try to make more of it.
129
So if I increase concentration of reactant, what happens?
When you increase the concentration of a reactant, the equilibrium shifts toward the products (right), favouring the forward reaction because the system tries to use up the added reactant to restore balance.
130
So if I decrease concentration of reactant, what happens?
When you decrease the concentration of a reactant, the equilibrium shifts toward the reactants (left), favouring the reverse reaction because the system tries to produce more of the reactant to restore balance.
131
So if I increase concentration of products, what happens?
When you increase the concentration of products, the equilibrium shifts toward the reactants (left), favouring the reverse reaction because the system tries to use up the added product to restore balance.
132
So if I decrease concentration of products, what happens?
When you decrease the concentration of products, the equilibrium shifts toward the products (right), favouring the forward reaction because the system tries to produce more of the product to restore balance.
133
So does enthalpy change matter in concentration questions?
not really....
134
What is a special note about Pressure and Le Chatelier's Principle?
A change in pressure will only affect equilibrium if there is an imbalance in the number of moles of gas on each side of the equation.
135
According to Le Chatelier's Principle, what happens when pressure is increased?
shift to the side with fewer gas molecules.
136
According to Le Chatelier's Principle, what happens when pressure is decreased?
shift to the side with more gas molecules.
137
What is the Haber process?
It is an industrial method for synthesising ammonia from nitrogen and hydrogen gases
138
What are the conditions required for the production of ammonia?
Iron catalyst
Pressure of 200atm
Temperature of 450 degrees celsius
139
Where are nitrogen and hydrogen sourced from?
Nitrogen = from the air
Hydrogen = from natural gas
140
What is the equation for the Haber process?
3H2 (g) + N2(g) reverse reaction sign 2NH3 (g)
141
What is the importance of the Haber process and getting ammonia?
Ammonia is crucial for fertilizers, which are essential for modern agriculture
142
What are the ideal conditions for the Haber process?
350 degrees celsius
400atm
143
Now considering the Haber process is a reversible reaction, how to be get the forward reaction to be favoured so ammonia gas can be produced?
Specific conditions
144
Why do we operate at different conditions in the Haber process than the ideal ones?
Temp; Perfect conditions are low temp but rate of reaction would be too slow so higher temperature settled for
Pressure; perfect conditions would be high pressure but costly and dangerous so lower pressure settled for
145
What are two ways that the rate of reaction could be increased in the Haber process?
-increasing temperature (however lowers yield)
-adding a catalyst (no effect on yield)
