Rates - everything

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what is the rate of reaction
the change in concentration of a reactant or product per unit time
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what can be used to measure the rate of reaction
a concentration-time graph
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what does the gradient on the graph tell us
the rate of reaction at a given time by drawing a tangent and working out the change in x over change in y
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what practical can be used to measure the rate of reaction
magnesium in HCl which produces hydrogen gas and magnesium chloride
titration - if all reactants are in solution
measure a decrease in mass on a balance
we could use a colorimeter
or use a pH meter
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what is the equation for rate of reaction
rate of reaction = change in concentration/ time
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what is a zero order
constant rate throughout and is not affected by concentration
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what is a first order
the rate is directly proportional to the concentration if we halve conc. the rate halves
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what is second order
rate is proportion to the square of the concentration if the conc. doubles the rate is times by 4
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what is the rate equation
rate = k [A]^x [B]^x [C]^x
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what is the equation for k
k = rate / [A]^x [B]^x [C]^j
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what is the overall order
it is the sum of the individual orders of all of the reactants
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what affect the rate of reaction
temperature, pressure or concentration
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what is a half-life
time taken for the conc. of a reagent to decrease by half
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what is the shape of the line on the conc.-time graph for half life for a zero order
straight line as it decreases with time
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what is the shape of the line on the conc.-time graph for half life for a first order
it is a curve and the gradient is proportional to conc. which gives us constant half lives
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how do you work out the rate constant from half lives
k = ln 2 / t1/2
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what is clock reaction
it is where you measure the time taken for a certain amount of product to form as you vary the conc. of one of the reactants
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what are assumptions we make in clock reactions
the conc. of the reactants does not change significantly over the timescale we are interested in
constant temperature
there is an endpoint
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what are different types of clock reactions
iodine clock test
sodium thiosulfate and the 'X'
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what is the equation for the initial rate
1/time
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rate-conc. graphs for zero order
the line is flat the conc. of the reactants do not affect the rate of reaction
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rate-conc. graphs for first order
line is a straight line throug the origins and the rate is directly proportional to the rate of reaction
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equation for rate constant for rate-conc. graphs
k = rate / conc.
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rate-conc. graphs for second order
it is a quadratic graph as the rate is proportional to the square of the conc.
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the rate constant for second order rate-conc. graphs
k = rate / [X]^2
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what is the rate determining step
is is the slowest step of a multistep reaction
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what is an intermediate
is a species which is formed in one step but used up in another it is not seen as a reactant or product in the overall equation
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what is in the rate determining step
the molecules in the rate equation
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what must chemist ensure when proposing a reaction mechanism
the RDS is given has the same number of molecules as the order for the reactants
the other step in the mechanism generate the product
all intermediates are used up
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what is the arrenhius equation
k = Ae^-Ea/RT
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how does the equation of a straight line correspond to the Arrenhius equation
y = c + mx
ln (k) = ln(A) - Ea/R 1/T
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what is a dynamic equilibrium
when the rate of the backward and forward reaction are the same, the conc. of products and reactants constant
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what is a
dinitrogen tetroxide which goes to nitrogen oxide
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what is a homogenous equilibrium
all chemicals are in the same state
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what is a heterogenous equilibrium
more than one state is present
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what is the equation for the equilibrium constatn
Kc = [C^c] [D^d] / [A^a] [B^b]
whihc is products / reactants
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what if there is no products what is the equation
it is 1 / prouduct^ order
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how can we measure the concentration of reactants
titrations, using a colorimeter
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what is the problem with titration
we have to use up the products or reacts and this will move the equilibrium, other chemicals may be present such as catalyst which may affect the titration
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what is the equation for mole fraction
mole fraction = number moles of substance A / total number of moles +
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what equation links the partial pressure and the mole fraction
partial pressure of substance A / total pressure of mixture = number of mole of sub A / total moles of all subtances
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what is the equation for partial pressure
partial pressure = mole fraction x total pressure
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what is the equation for Kp
Kp = p(C^c) (D^d) / p(A^a) (B^b)
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what is the reaction quotients
it is the constant at all times for Kc and Kp but if not at equilibrium not equal to Kc o Kp
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why do catalyst affect the equilibrium
they do not affect the equilibrium as they increase the rate of the forwards and backwards reactions by the same amount
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Card 2

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what can be used to measure the rate of reaction

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a concentration-time graph

Card 3

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what does the gradient on the graph tell us

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Card 4

Front

what practical can be used to measure the rate of reaction

Back

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Card 5

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what is the equation for rate of reaction

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