describe zero order reactions
-when the concentration of a reactant has no effect on the rate
equation for zero order reactions
rate ∝ [A]^0
equation for first order reactions
rate ∝ [A]^1
equation for second order reactions
rate ∝ [A]^2
describe first order reactions
-when the rate depends on the reactions concentration change raised to the power of 1
-whatever number the concentration goes up by, the rate goes up by the same number
describe second order reactions
-when the rate depends on the concentration change to the power of 2
-whatever happens to the concentration, the rate increases by that number squared
rate equation
rate = k[A][B]
how do you calculate overall order
-look at the rate equation and add up the powers of the square brackets
describe how to calculate orders from experimental results
-choose where the reactant you are not working out stays the same
-this means the reactant you are working out is responsible for the change in rate
-the reactant doesnt have to stay the same in two experiments in a row (can be anywhere on the table)
describe how to calculate orders from experimental results when there is nowhere where the other reactant stays the same
-calculate change in conc for all reactants at any point
-calculate change in rate at this point
increase in rate/effect on rate of known reactant = effect on rate of unknown reactant
-compare the effect on rate to the effect on concentration to work out order
describe how to calculate the rate constant from experimental data
-rearrange into k = rate / [A][B]
-choose any experiment and values from this substituted in
-rate constant for one reaction is the same for all of them
-work out units
describe how to calculate blank values on a table of experimental data when equation given
-work out orders and use from here
name the methods for working out order using experimental data
- continuously monitor the change in concentration of A against time
- use initial rate method to find out how the initial rate changes as you vary the concentration of A
describe the continuous monitoring methods
-loss in mass
-volume of a gas
-pH changes - use pH probe and data logger
-colorimetry
describe how to choose which continuous monitoring methods should be used
depending on the question
eg if an acid or base in question, pH change can be measured
describe the zero order concentration-time graph
-produces a straight line with a negative gradient
-the reaction rate does not change at all throughout the course of the reaction
describe the first order concentration-time graph
-produces a downward curve with decreasing gradient over time
-as the gradient decreases with time, the reaction gradually slows down
describe the second order concentration-time graph
-downward curve but steeper at the start and tails off more slowly
describe how to calculate the rate of a zero order concentration-time graph
-calculate gradient for rate
rate=k
describe how to calculate the rate of a first order concentration-time graph
-calculate gradient at time given for tangent, or at t=0 for initial rate
-if need to work out k -> put into rate equation
describe how to calculate the rate of a second order concentration-time graph
-same methods as first order
why is half life needed to distinguish between first and second order graphs
-the curves can look similar
define half life
-the time taken for half of the reactant to be used up
half life of a first order reaction
-constant, independent of the initial concentration
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Module 2 - Atoms, Ions and Electronic Structure44
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Module 2 - Amount of Substance60
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Module 2 - Bonding And Structure66
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Retrieval Practice3
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Module 4- Basics of Organic Chemistry65
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Module 2 - Acids and Redox65
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Module 4 - Alkanes35
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Module 4 - Alkenes45
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Module 3 - Periodicity43
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Module 3 - Group 218
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Module 3 - Halogens59
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Module 3 - Qualitative Analysis21
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Module 4 - Alcohols34
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Module 3 - Enthalpy Changes50
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Module 4 - Organic Synthesis10
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Module 4 - Haloalkanes19
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Module 3 - Rates of Reaction55
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Module 4 - Synthetic Routes19
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Module 5 - How Far17
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Module 6 - Aromatic Chemistry57
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Module 5 - Acids, Bases, Buffers55
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Module 5 - How Fast24
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Module 5 - Energy51
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Module 5 - Redox and Electrode Potentials32
