Rate Equations Flashcards
(23 cards)
Define the term rate of reaction
Change in concentration of any product or reactant per unit time
At a given instant, how could you calculate the rate of a reaction
Change in concentration divided by change in time
How could you measure the rate of reaction experimentally
Use a colorimeter at suitable intervals if there is a colour change
If gas is evolved, use a gas syringe to collect volume if gas evolved, or measure the change in mass of the reaction mixture
How would you measure the rate of reaction for a really fast reaction
Use a flash of light to break bonds, use probe flashes to record amount of light absorbed by a species, this can show its concentration
How can you determine the rate constant and rate expression for a reaction
Only experimentally
What affects the value of the rate constant for a given reaction
Temperature
Generic rate expression
Rate = k [X]^x [Y]^y
Do species need to be in the chemical equation to be in the rate expression
No
Define the term order of a reaction with respect to a given product
The power to which a species’ concentration is raised in the rate equation
Define the term overall order of reaction
The sum of the orders of reaction of all species I the rate expression, total order
How would you draw a rate concentration graph
Plot [A] against time, draw tangents at different values
Draw a secondary graph of rate against [A]
Rate concentration graph for a zero order reactant
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Rate concentration graph for a first order reactant
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How could you confirm that a reactant is second order
Graph of rate against concentration squared would be a straight line through the origin
How could you fine the rate expression using the initial rate method
Do a series of experiments, during which you vary concentrations so the concentrations of just one reactant changes each time
Plot a graph, draw a tangent at t=0 to find the initial rate
Compare rates and concentrations between each experiment to find order of reactants and overall rate equation
What must you add to react with the I2 as it is produced for an iodine clock reaction
Known moles of sodium thiosulfate and a little starch
Reacts with I2 in 1:2 ratio
When does the starch turn a blue black in an iodine clock reaction and why
When all of the Na2S2O3 has been used up and so I2 is produced, which reacts with starch leading to a blue black colour
How can you calculate the rate of reaction from the data from an iodine clock reaction
Record time taken for colour change to occur
Use rate = 1/t
What is the effect of a 10k temperature increase on the rate of reaction
Double rate of reaction
What is true of the half life of a first order reactant
Half life is constant
What is the Arrhenius equation
k = Ae^-Ea/RT
How can you convert the Arrhenius equation into a useful form
K = -Ea/RT + ln A
What is the rate determining step
The slowest step in a reaction mechanism, which determines the overall rate of reaction
