Rates, equilibrium and pH Flashcards
Define the rate of reaction
the change in concentrations of a reactant or a product per unit time
Define the rate constant
this is the constant that links the rate of reaction with the concentrations of the reactants raised to the powers of their orders in the rate equation
Write the rate of reaction equation
change in concentration of reactant or product/ time
Describe zero order
if the order is 0 with respect to reactant A then the rate [a]^0
- the rate is unaffected by changing concentration of A
- any number to the power 0 is equal to one
Describe first order
if the order is 1 with respect to reactant B then the rate [B]^1
- rate is directly proportional to concentration
- if [B] increases by 2 times the rate also increases by 2 times
Describe second order
if the order is 2 with respect to C then the rate is [C]^2
- the change in rate will be equal to the concentration squared
For example
- if [C] increases by 2 times, the rate increases by 4 times
- if [C] increases by 3 times the rate increases by 9 times
Write out a rate equation with letters
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Does a zero order appear in the rate equation
A 0 order will not appear in the rate equation as it does not affect the rate of reaction
Do you show the power of 1 in the equation
NO
How do you work out the overall order
An overall order is the sum of individual orders
Write down the units of rate constants
Zero order - moldm-3s-1
First order - s-1
Second order - dm3mol-1s-1
Third order - dm6mol-2s-1
What do you measure in reactions involving acids or bases
- pH changes by carrying out titrations
- pH changes by using a pH meter
What do you measure in reactions involving gases
- change in volume or pressure
- loss in mass of reactants
What do you measure in reactions that produce visual changes that we observe
- formation of a precipitate
- colour change
How do you work out the rate using a graph
rate = change in concentration/ time taken for change to take place
What is a half life
this is the time taken for concentration of a reactant to decrease by half
Write the symbol for half life
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Draw the concentration - time graph for zero order reactions
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Draw the concentration-time graph for first order reactions
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Write the equation that uses the half life to find the rate constant
k= ln2/ half life
How do you work out t=o (initial rate)
find the gradient of the tangent at 0
How do you use the initial rate to determine the order to reactions
- To determine the order of reaction vary the concentrations of the reactant several times and obtain the initial rate each time then plot the results on a graph to determine the order
The time taken for the visible event to occur is …
inversely proportional to the initial rate, the shorter the time taken for change the faster the reaction is
1/t
DRAW THE RATE-CONCENTRATION GRAPH FOR ZERO ORDER
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DRAW THE RATE-CONCENTRATION GRAPH FOR FIRST ORDER
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DRAW THE RATE-CONCENTRATION GRAPH FOR SECOND ORDER
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