Module 3 (Reactive Chemistry) Flashcards
1
Q
What are the 5 common ways to observe a chemical change?
A
A solid is formed (precipitate)
A gas is evolved
Permanent change of colour
Disappearance of solid
Significant change in temperature
2
Q
What is a physical change? What is an example?
A
Physical changes are changes affecting the form of a chemical substance, but not its chemical composition. In a physical change, there is no new substance formed and physical changes are easily reversible
An example of this is the boiling of water in which the form of the chemical changes from a liquid to a gaseous state, and no chemical bonds were broken in the process. It is also easy to reverse with little energy
3
Q
What is a chemical change? What is an example?
A
a usually irreversible chemical reaction involving the rearrangement of the atoms of one or more substances and a change in their chemical properties or composition, resulting in the formation of at least one new substance.
Another definition could be the breaking down and rearrangement of chemical bonds.
An example of this is the electrolysis of water (Turning water into hydrogen and oxygen molecules), in which chemical bonds are being broken and rearranged. However, it is hard to reverse and requires a lot of energy
4
Q
List three advantages of using models for chemistry
A
Any of the three:
Models can communicate observations and ideas to other people
Models help visualise ideas or abstract concepts
Models can be used to make and test predictions
Can be used to help illustrate and explain scientific theories or prove them wrong
5
Q
List three disadvantages of using models for chemistry
A
Any of the three:
Don’t include all the details of the objects they represent
Models don’t behave like the things they represent
Accuracy is lost when trying to simplify things into a model
Approximations are used
6
Q
Why do chemical reactions exist?
A
They exist because the law of conservation of mass states that matter can be neither created nor destroyed but merely changed from one form to another. In a chemical reaction, mass is conserved through the balancing of both sides so that the number of atoms of each element is conserved
7
Q
What is a chemical reaction?
A
a process in which one or more substances, the reactants, are converted to one or more different substances, the products.
8
Q
How is a chemical reaction formatted?
A
Reactants on the left side and products on the right side.
Reactants —–> Products
9
Q
What are the three ways of representing chemical reactions?
A
Word equations - Chemical names only
Symbolic/ Chemical equations - Chemical Formulae only
Balanced Chemical equations - Number prefixes and states
Need to practice irl
10
Q
What are the different state symbols?
A
Solids - ‘S’
Liquid - ‘l’
Gas - ‘g’
Aqueous (dissolved in water - ‘aq’
11
Q
What is a synthesis/combination reaction? What would the general equation look like?
A
This reaction is where two reactants produce a single product. This reaction is typically accompanied with a release of energy in the form of heat and/or light
A + B —> AB
12
Q
What are some (2) examples of synthesis reactions?
A
Hydrogen + Oxygen —> water
Magnesium + Oxygen —> Magnesium oxide
13
Q
What are decomposition reactions? What would the general equation look like?
A
These are basically the opposite of synthesis reactions. Here, the reaction is where a compound is decomposed into two or more other substances. These decomposed substances can be elements or other compounds
AB —> A + B
14
Q
What is an example of a decomposition reaction
A
Silver Bromide —> Silver + Bromine
15
Q
What are the three types of decomposition reactions?
A
Thermal
Electrical
Light
16
Q
Where can the energy required for decomposition reactions be derived from?
A
Heat, light or electricity
17
Q
What is thermal decomposition?
A
Thermal decomposition is caused by heat. In this reaction, a chemical reaction occurs when a compound breaks down when heated. It is endomorphic
18
Q
What is an example of thermal decomposition?
A
Copper Carbonate + Heat (In an equation, don’t have to mention) —> Carbon dioxide + Copper oxide
19
Q
What is electrical decomposition?
A
Electrical decomposition is caused by electricity. In this reaction, an electrical current is passed through a liquid or solution to induce a chemical reaction
20
Q
What is an example of electrical decomposition?
A
Electrolysis of water.
Water + electricity (In an equation, don’t have to mention) —> Hydrogen + Oxygen
21
Q
What is light decomposition?
A
This type of decomposition is caused by light/photons. In this reaction, light or photons are used to break the reactants to form several products
22
Q
What is an example of light decomposition?
A
Silver chloride +light photons (In an equation, don’t have to mention) —> Silver + Chlorine
23
Q
What is a combustion reaction?
A
Combustion reactions are reactions in which substances react with oxygen and heat is released. It can often be referred to as an oxidation reaction. Typically a combustion reaction will involve a hydrocarbon. Combustion is a self sustaining chemical reaction that occurs at temperatures above those of the surroundings
24
Q
What are (3) characteristics of combustion?
A
Emission of large quantities of heat and light (exothermic)
Formation of new substances
Inability to reverse the reaction
25
What does combustion of hydrocarbons produce?
Carbon dioxide and water (as long as there is enough oxygen)
26
What are hydrocarbons?
Compounds which contains mostly the elements carbon and hydrogen
27
What are the three different types of hydrocarbons?
Alkanes, Alkenes, Alkynes
28
What are alkanes and their properties? (4)
Alkanes are saturated (meaning that all carbon atoms hold the highest allowed amount of hydrogen atoms). All the bonds between hydrogen and carbon are single bonds. The general formula is C(n) H(2n+2). The suffix is -ane
29
What are alkenes and their properties? (4)
Alkenes are unsaturated (meaning that all carbon atoms do not hold the highest allowed amount of hydrogen atoms). In alkenes, there is at least one carbon to carbon double bond. The general formula is C(n) H (2n). The suffix is - ene
30
What are alkynes and their properties? (4)
Alkynes are unsaturated (meaning that all carbon atoms do not hold the highest allowed amount of hydrogen atoms). In alkynes, it consists of at least one carbon to carbon triple bond. The general formula is C(n) H(n). The suffix is -yne
31
How are alkanes named?
They are named by combining a prefix which describes the number of carbon atoms in the molecule with the root ending 'ane'
32
How are alkenes named?
They are named by combining the prefix which describes the number of carbon atoms in the molecule with the root ending 'ene'
33
What are the 'stem names' for the numbers of carbon atoms in a hydrocarbon chain (1-10)
1 - meth-
2- eth-
3- prop-
4- but-
5- pent-
6- hex-
7- hept-
8- oct-
9- non-
10- dec-
34
What are complete combustions?
In complete combustions, products are only carbon dioxide and water.
Fuel + oxygen ---> carbon dioxide + water (and energy)
35
What are the 4 steps in writing balanced equations?
1. Write the word equation
2. Write the chemical formulae
3. Balance coefficients in front of each chemical
4. Add state symbols
36
What are incomplete combustions?
Incomplete combustions occur when there is insufficient oxygen to completely react with fuel. Incomplete combustions is inefficient as it does not use the full energy content of the fuel. Here, the amount of fuel consumed is dependent on how much oxygen is available. It produces environmental pollutants such as carbon and carbon dioxide
37
What are the products of an incomplete combustion (in a reaction)?
In an incomplete combustion the products may include carbon monoxide, carbon dioxide or carbon, and water.
In other words the product of an incomplete combustion can be any of these: carbon, carbon monoxide, carbon dioxide (we pick which one(s) we want to be the product), PLUS HAVE TO INCLUDE water. SO PICK ANY OF THE CARBONS PLUS WATER
I.e. combustion of methane could result in carbon and water; carbon, carbon dioxide and water; carbon, monoxide, carbon dioxide and water; carbon dioxide and water.
38
What is a precipitate?
A precipitate is an insoluble salt
39
Why are some substances insoluble?
Some substances will be insoluble if the intermolecular forces between the substance and the water are weaker than those between the solute particles by themselves and the forces between the water molecules themselves
Because of this, ionic lattices stay together, the ions don't dissociate and the substance remains a solid
40
What are solutes?
The substancethat dissolves in a solvent to produce a homogeneous mixture.
41
What are solvents?
A substance that has the ability to dissolve a given solute to form a solution with it
42
What is a precipitation reaction?
A precipitation reaction is a type of double displacement reaction, where there is the formation of an insoluble substance
43
What causes a precipitation reaction?
When solutions of two ionic substances are mixed, precipitation occurs if one type of positive ion present is able to combine with another type of negative ion present to form an insoluble substance
44
What are neutral species equations? Example using sodium chloride and silver nitrate
Neutral Species equations are the normal chemical reaction equations.
I.e. 2NaCl (aq) +Ag(NO3)2 (aq) ---> 2NaNO3(aq) +AgCl2 (s)
Where silver chloride is the precipitate
45
What are complete ionic equations? Example
Complete ionic equations are where each compound is broken up into their disassociated ion equivalents except for the precipitate on the products side (i.e. NaCl would turn into Na^2+ + 2Cl^-)
I.e. 2Na+ + 2Cl- + Ag2+ + 2(NO3)- --> AgCl2 + 2Na+ + 2(NO3)-
46
What are Net ionic equations? Example using sodium chlroide and silver nitrate
Net Ionic equations are basically complete ionic equations, however, the spectator ions are removed (The ion is unchanged on both sides of a chemical equation)
I.e. (following from the sodium chloride and silver nitrate example)
2Cl- + Ag2+ + ---> AgCl2
47
What is a saturated solution?
A saturated solution is one in which no more of a particular solute can be dissolved in a given quantity of solvent at a specified temperature
48
What is an unsaturated solution?
Basically the opposite of a saturated solution and is one where there is not as much of a particular solute being dissolved in a given quantity of solvent at a specified temperature
49
What is the concentration of a solution?
The concentration of a solution is the amount of solute present in a specified amount of solvent or solution
50
What is an equilibrium?
When a solution becomes saturated, ions still continue to break away from crystals of solid and go into solution, however at the same time an EQUAL number of ion pairs from solution go on to the solid.
This situation is referred to as equilibrium
51
What symbol indicates equilibrium?
The 'state rail' sign indicates equilibrium. The state rail is basically a sign that looks like half an arrow pointing one way, and another half of an arrow pointing the other way
52
State the solubility rules regarding substances which are SOLUBLE
Eight
All Nitrates
All Acetates
All Sulfates (except calcium, barium, lead, mercury and silver)
All Chlorides, bromides, iodides (Group 7)(except lead, mercury and silver)
All ammonium compounds
Group 1 metals
53
What are the exceptions to sulfates and chlorides, bromides, iodides being soluble?
Sulfates - Calcium, lead, mercury, silver, barium
Chloride, bromides, iodides - Lead, Mercury, Silver
54
State the solubility rules regarding substances which are INSOLUBLE
5
All carbonates (except sodium, potassium, ammonium)
All oxides and hydroxides (except sodium, potassium, calcium, magnesium and barium)
All sulfides (except sodium, potassium, magnesium, calcium, barium and ammonium)
All phosphates (except sodium, potassium and ammonium)
55
What are the products of an acid and reactive metal reaction? Give the layout of the equation
I.e. Magnesium Hydrochloric acid
The products are metal salt typically in the aqueous state (double check) and hydrogen gas
Acid + Metal --> Salt + hydrogen gas
56
What are the products of an acid and base reaction? Give the layout of the equation
I.e. Sodium hydroxide and Hydrochloric acid
(Known as a neutralisation reaction)
The products are Metal salts and water
Acid+ Metal hydroxide (base) --> Salt + water
57
What are the products of an acid and a metal carbonate reaction? Give the layout of the equation
I.e. Sulfuric acid and calcium carbonate
The products are metal salts, carbon dioxide gas and water.
Acid+ metal carbonate --> Salt + carbon dioxide gas + water
Note: the products of acid carbonate and acid hydrogen carbonate reactions are the same
58
How are the 'salts' calculated in a chemical reaction?
They are calculated by combining the anions and cations of the first and second reactants which won't produce any of the products which are guaranteed to have to be the product
I.e. Na + HCl:
H2 would be the guaranteed product, and the rest would combine to give a salt
59
What are displacement reactions?
Displacement reactions occur when a more reactive metal displaces a less reactive metal and takes its place in a compound (the two switch)
I.e. Cu + 2AgNO3 --> 2Ag + Cu (NO3)2
This occurs because the copper is more reactive than silver
60
How does reactivity of metals determine if a displacement reaction occurs?
This is because the more reactive the metal, the more likely it is to lose its electrons
61
What is the order of the reactivity series? From most reactive to least reactive. (16)
Potassium
Sodium
Lithium
Calcium
Magnesium
Aluminium
Zinc
Iron
Tin
Lead
Hydrogen
Copper
Mercury
Silver
Gold
Platinum
62
What is a mnemonic to remember the reactivity series? (16)
Hint: Has something to do with animals
Please - Potassium
Send - Sodium
Lions - Lithium
Cats - Carbon
Monkeys - Magnesium
And - Aluminium
Zebras - Zinc
Into - Iron
Lovely - Lead
Hot - Hydrogen
Countries - Copper
Signed - Silver
General - Gold
Penguin - Platinum
63
What is a redox reaction?
They are 'electron transfer reactions'
64
What are the products of a metal and oxygen reaction?
Give a general equation
The product is a metal oxide
Equation: Active metal + oxygen --> metal oxide
65
How does the reactivity of metals affect the metals reactions with oxygen
The more reactive it is, the less heat is required to make it react with oxygen
66
What 4 elements react slowly at room temperature but burn vigorously if heated?
Magnesium, Aluminium, Zinc and Iron
67
What three elements react slowly with oxygen and only if heated?
Tin, Lead, Copper
68
What three elements have no reaction with oxygen?
Gold, Platinum, Silver
69
What three elements have no reaction with oxygen?
Gold, Platinum, Silver
70
What are three properties of metal oxides?
They are ionic compounds
They are basic oxides
Metal oxides generally dissolve in water to form hydroxides
71
How does the reactivity of metals affect the reaction of metals and water?
The more reactive metals are able to react with just cold water, whereas the less reactive metals only react with hot water or steam
72
What is a general equation for a metal and water reaction?
Reactive metal + water ---> Hydrogen + Metal hydroxide
73
What 5 elements react with water at room temperature?
Lithium, Sodium, Potassium, Calcium and Barium
74
What 4 elements will react with steam?
Magnesium, Aluminium, Zinc, Iron
Note: product is metal oxide not metal hydroxide unlike the water reaction (still have the hydrogen)
75
What 6 elements won't react with any form of water?
Tin, Lead, Copper, Silver, Gold, Platinum
76
What does OIL RIG mean in redox reactions?
Oxidation = Loss of electrons
Reduction = Gain of electrons
Just a mnemonic
77
What occurs in an oxidation reaction?
Loss of electrons
78
What occurs in a reduction reaction?
Gain of electrons
79
What are half equations?
Half reaction equations are a method of balancing redox reactions
80
What happens in an oxidation half equation? Give examples
(For elements which are cations) In an oxidation half reaction, there is the element on the left before an arrow. On the right hand side (products), there will be the ion form of the element on the left plus the amount of electrons that it takes to bring the ion back to the element form.
I.e. Na(s) --> Na+(aq) + e-
Note: The oxidation number is simply the amount of valence electrons that the element has
81
What happens in a reduction half equation? Give examples
On the left hand side, there is the element as well as electrons (enough to turn the element into it's ion counterpart). On the right there is the ion of the element
I.e. Cl2(g) + 2e- ---> 2Cl- (aq)
Another question that may be asked is the reduction of an ion. Here, there is the ion (typically a cation) which is added with as many electrons as required to turn the ion back into an element. On the right hand side is the element
82
What can redox reactions be used for?
Chemical reactions that produce electrical energy in batteries are redox reactions. In batteries, electrons are transferred from one reactant to another through the wires that make up the electric circuit
83
What is an oxidising agent or an oxidiser?
An oxidiser or oxidising agent oxidises something else, therefore it, itself is reduced
84
What is a reducing agent or reducer?
A reducing agent or reducer reduces something else, therefore it, itself is oxidised
85
Why do oxidation numbers exist?
Because not all redox reactions are easy to identify, so scientists assigned oxidation states (numbers) to atoms which help track the number of electrons transferred in a redox reaction
86
What is an oxidation number?
An oxidation number is the charge, real or imagined that an atom would have if it occurred as an ion in a compound. They are typically equal to the charges.
87
What is the oxidation number of an atom in the elemental state?
Zero
88
What is the oxidation number of a monatomic ion? (A monatomic ion is an ion consisting of exactly one atom)
It is equal to its charge
89
what is the algebraic sum of the oxidation numbers in the formula of a compound equal to?
Zero
90
What is the oxidation number of hydrogen in a compound? What is the exception?
1+, except when hydrogen forms compounds called hydrides with active metals, and then it is 1-
91
What is the oxidation number of oxygen in a compound? What are the exceptions?
2-, except in peroxides when it is 1- (two O's)
I.e. H2O, the oxygen is 2-, but in H2O2, it is 1-
92
What is the sum of oxidation numbers in the formula for a polyatomic ion equal to?
It is equal to the charges on that ion.
I.e, in the sulfate ion, the sum of the oxidation numbers in the formula is 2-, and the oxygens and sulfur add up to 2-, where the oxygens are 2- each, and the sulfur is thus 6+
93
What is a galvanic cell?
A galvanic cell is a device that makes a chemical reaction occur in a way that generates electricity.
94
How are redox reactions used in galvanic cells?
They allow for the arranging of the oxidation and reduction half reactions to occur at different locations, and provides a wire for the electrons to flow through which creates an electrical current
95
Are the more reactive metals oxidised or reduced in both chemical equations, redox reactions and galvanic cells?
More reactive metals will be oxidised, whilst less reactive metals will be reduced
96
What is the structure of a galvanic cells?
Consists of two half-cells linked by an external metal conductor and an internal salt bridge
97
What are half cells?
Half cells are physically separate compartments where oxidation and reduction occur
98
How do you draw a galvanic cell? (7)
1. Draw two beakers with the metal solutions (i.e., on the left hand side, could have zinc nitrate, and on thee right hand side, could have copper nitrate)
2. Draw the anodes and cathodes which are simply the metals 'dipped ' in their respective solutions
3. Draw a connecting 'salt bridge' (typically is KNO3)
4. Draw a 'wire' linking the tops of the anodes and cathodes, with a voltmeter in the middle
5. Draw an arrow indicating the flow of electrons (The arrow will have it's origin at the site of oxidation (anode)(More reactive metal), and it's head at the site of reduction (cathode)(less reactive metal)
6. Draw half equations of what's happening in each beaker below
7. Show where the anions and cations are moving to in the salt bridge
99
What happens as time goes on in a galvanic cell? Why? (4)
The strip of anode metal will slowly dissolve (Because the anode metal is constantly being oxidised into the metal ion and electrons), and will eventually disappear
The metal form of the cathode will be deposited onto the metal cathode (Because it is the side of reduction, and the electrons which come from the electron flow will help reduce the metal ion into the metal form)
The cations in the cathode solution will decrease (Because the cations are constantly being reduced by the incoming electrons which decreases the cations in the less reactive solution)
The cations in the anode solution will increase (Because the metal is constantly being oxidised into cations and electrons, however the electrons are travelling through the wire to the cathode, and no electrons are left to react with the cations, thus build up of cations)
100
What is the cathode and anode?
Cathode - the site of reduction (less reactive metal side). The electrode where reduction takes place
Anode - the site of oxidation (more reactive metal side). The electrode where oxidation takes place
101
What is an example of what changes occur as time goes on in a galvanic cell. With relation to the example of Copper and Silver
When drawing the chemical reactions which are occurring in a galvanic cell of Copper (More reactive), and silver(less reactive), the following changes can be observed:
Metallic silver deposits onto the silver strip
Some of the copper strip dissolves
The [Ag+] in the beaker decreases
The [Cu2+] in the other beaker increases
102
What is an electrode?
An electrode is a conductor of a cell which gets connected to external circuits
103
What is a salt bridge?
An electrolyte or electrolyte gel which joins two half-cells to complete the circuit in a galvanic cell and allows for the movement of ions to maintain a balance of charges.
104
What is the role of the salt bridge?
The salt bridge contains a solution of relatively unreactive electrolytes, and because of this, these ions are free to move so that they can balance the charges formed in the two half-cells. This process involves the cations in the salt bridge moving towards the cathode, while anions in the salt bridge move towards the anode
Without the salt bridge, there will be a build up of positive or negative charges, which will prevent further reactions to occur
105
What is galvanic cell notation?
It's a shorthand form of representing cells
106
In galvanic cell notation, what does '/' denote?
It denotes a change in phase ( metal in contact with ion)
107
In galvanic cell notation, what does '//' denote?
It denotes a salt bridge
108
What is EMF (Electromotive force)?
This is the potential difference (voltage) across the electrodes of the cell. It is the maximum voltage that the cell can deliver.
109
What is a reduction potential?
They are a measure of the relative tendency of a substance to gain one or more electrons compared to the normal hydrogen half cell
110
What is E^0?
Standard reduction potential, also known as e-nought
111
Does having a negative volt on the standard reduction potentials sheet indicate a strong reducing or oxidation agent?
Strong reducing agent (Reduces others, oxidises itself) (typically more reactive)
112
Does having a positive volt on the standard reduction potentials indicate a strong reducing or oxidation agent?
Strong oxidation agent (Oxidises others, reduces itself) (Typically less reactive)
113
How could you utilise the standard potentials sheet to determine the reactivity of metals?
Since the negative volts indicate a strong reducing agent, that means it will be the most reactive, (Because most reactive is most likely to be oxidised) and as the negative volts get smaller (towards zero) and then pass zero into positive numbers, then it indicates less reactive elements.
114
How do you form a redox reaction given two half reactions?
Literally add them together, whilst balancing the electrons, remember, there should be both oxidation and reduction occurring
115
How do you calculate EMF of a given equation?
Given an equation, break it down into its half reactions. The total EMF is the sum of E-nought value of the reduction and then the E-nought value of the oxidation.
116
What are dependent variables?
Dependent variables are the factors which are observed or measured
117
What is reliability? How do you improve it in an experiment?
When a scientist repeats an experiment with a different group of people or a different batch of the same chemicals and gets very similar results then those results are said to be reliable. To improve reliability, it has to be done several times and get similar results
118
What is accuracy? How do you improve it in an experiment?
Accuracy describes how well a measuring instrument determines the variable it is measuring. Greater accuracy can be achieved by using accurate measuring instruments and picking instruments which is an appropriate measure of accuracy.
119
What is validity? How do you improve it in an experiment?
Validity describes whether the results of an experiment really do measure the concept being tested, discuss whether or not the results are actually helpful. It could be improved through picking a correct experiment to test out a hypothesis about a certain subject.
120
Does doubling the half reactions (to balance electrons) alter the E-nought value?
Doubling the half reaction does NOT change the E-nought value
121
What are homogenous reactions?
Reactants are in the same phase (I.e state such as liquid or aqueous)
122
What are heterogenous reactions?
Reactants are in different phases (I.e. reactants are in different states such as a solid and liquid reacting together)
123
What does collision theory state?
In order for a chemical reaction to take place, the reactant particles must:
Collide with the right orientation
Collide with sufficient energy (Above the activation energy barrier)
Note: both of these must be achieved, not only one for a successful chemical reaction
124
Why do reactant particles have to collide with the right orientation? Give an example using the formation of a chlorine gas molecule from a singular chlorine atom and chlorine nitrite
To ensure that bonds can be broken and reformed. I.e., the new molecule which is meant to be formed actually have to have the parts of the new molecule hitting each other, it can't be a different atom hitting it as it will create a different molecule which isn't wanted
If The Nitrogen atoms hit the chlorine atom, they can't form Cl2, so that's an example of wrong orientation, however, if the chlorine atom hits the chlorine atom, then it will be able to form Cl2.
125
What is activation energy?
Activation energy refers to the minimum amount of energy which is required for a chemical reaction to take place.
It can be thought of a 'barrier' that stops reactants from being converted into products, thus energy must bee supplied to reactants to enable them to form the products
126
What symbol represents activation energy, and how is it expressed (i.e. units)
E with a subscript 'a'
Is expressed in KH mol ^ -1
127
What are endothermic reactions?
Chemical reactions wheere the reactants absorb energy from the surroundings
128
What are exothermic reactions?
Chemical reactions which releases energy into it's surroundings, typically in the form of heat
129
What is the relationship between endothermic reactions and activation energy?
Energy must be continuously supplied to reactants to form the activated complex as energy is absorbed by the bond-making process
130
What is the activated complex?
The intermediate step between reactants and products
131
What is the relationship between exothermic reactions and activation energy?
The overall release of energy into the environment can be used by reactants to reach the activated complex; thus the reaction becomes self-sustaining
132
What factors can impact the rate of reaction in homogenous reactants? (3)
Increasing the concentration of reactants
Increasing the temperature
Using a catalyst
133
What factors can impact the rate of reaction in heterogenous reactants? (5)
Increasing the concentration of reactants/increasing pressure of gasses
Increasing the temperature
Using a catalyst
Increasing surface area of reactants
Increasing rate of mixing/stirring (kind of)
134
How does temperature affect the reaction rate?
An increase in temperature increases the average kinetic energy of the reactant molecules, and changes the distribution of molecular kinetic energies. The increased velocities of the molecules leads to greater collision and thus faster rate of reaction
135
How does an increase in temperature affect the graph?
The graph flattens a bit, as the temperatures increase kinetic energy, and increases the percentage of molecules which can reach the activation energy
136
How does concentration affect reaction rates?
Increasing concentration of reactants in solution increases the rate of reaction as there are a greater number of particles available to react. Thus increasing the frequency of collisions between particles
137
What is concentration?
The amount of a substance in a space
138
What does increasing pressure in gases do?
Increases the concentration, and thus increases the rates of reaction
139
How does surface area affect reaction rates?
Increasing the surface area of solid reactants increases the number of particles that are exposed and are available to react and thus increases the frequency of particle collisions, increasing rate of reaction
140
How do catalysts affect reaction rates?
A catalyst is a substance that provides an alternative pathway with a lower activation energy for reactants to form products, therefore increasing the rate of chemical reactions, whilst catalyst remains unchanged at the end of the reaction
141
How does stirring affect reaction rates?
Stirring keeps reactant particles in continual motion, thus increasing the chances of collision , and increasing rate of reaction
142
What is a catalyst?
A substance that provides an alternative pathway with a lower activation energy for reactants to form products, however it is not actually involved in the chemical reaction
143
What happens to the graph when catalysts are introduced?
The Activation energy is moved to the left (or at least towards a less kinetic energy (on the x-axis))
144
What trends do the trends of reactivity follow (i.e. electronegativity)? (3)
Electronegativity. ionisation energy, atomic radius
145
What does the collision theory say about solids?
particles are close together and vibrating in fixed positions, has a definite shape, definite volume and cannot be compressed or diffused
146
What does the collision theory say about liquids?
Particles are close together but they are moving more freely - rolling and sliding over each other, they shape will depend on the container, it has a definite volume, cannot be compressed and can diffuse(spread through another substance)
147
What doeees the collision theory say about gases?
Particles are far apart and moving very freely and rapidly, the shape depends on the container fits all available space and can be both compressed or diffused
148
Does the state of a substance affect rate of reaction?
Yes
149
What happens if you attempt to make two solids react?
tend to react very slowly, if they even do react. Solid particles can only vibrate in a fixed position, so particles will not come into contact with enough force to allow them to react
150
What happens if you attempt to make a solid and a liquid/gas react?
They will react, especially if solid is cut into small pieeces
151
What happens if you attempt to make solutions of ionic chemicals react?
React very quickly as their ions are ready to react, and are also free to move within the solution. Particles of a liquid are continually moving and coming into contact with each other
152
What happens if you attempt to make gas particles react?
They tend to react even faster because their particles are moving freely at high speeds, however, they also tend to be further apart
