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Flashcards in Rate Equations Deck (23)
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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



Generic rate expression

Rate = k [X]^x [Y]^y


Do species need to be in the chemical equation to be in the rate expression



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



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