rates + equilibrium Flashcards
order of reaction definition
shows the extent to which the concentration of a reagent affects the rate of reaction
the power to which the concentration of a reagent is raised to in the rate equation
what does it mean if a reagent is 0 order
the rate is unaffected by changes in concentration of that reagent
what does it mean if a reagent is 1st order
if the concentration changes, the rate will change by the same factor/amount
what does it mean if a reagent is 2nd order
if the concentration changes, the rate will change by the square of that amount
rate constant k definition
the constant of proportionality in the rate equation
what affects rate constant k
temperature and catalysts, not concentration or pressure
how does temperature affect k
increase in temperature increases k value
- high temp = more kinetic energy = more successful collisions = high rate = larger k value
how do catalysts affect k
catalysts increase k
- catalyst = faster rate = larger k value
what does a very high k value mean
fast reaction rate
what does a very small k value mean
slow reaction rate
what is the overall order of a reaction
the sum of all orders of reagents taking part in reaction
half life definition
how long it takes for reactant concentration to half
what can be found from concentration-time graphs of a reaction
the order of the reactant can be found by measuring the half life
- if half life gets smaller = 0 order
- if half life stays constant = 1st order
- if half life increases = 2nd order
which step of a reaction is the rate determining step
the slowest step, as a reaction can only go as fast as the slowest part of a reaction
if the gradient of a first order rate-conc graph is measured what does this give
the value of k
this is because rate = k[reactant] so as conc = x axis and rate = y axis gradient = k
when determining composition of a reaction mixture, why is the analysis of a physical property preferable to a chemical analysis
- measuring the change in a physical property will not interfere with reaction
- chemical analysis means the reaction must be stopped so analysis can take place to determine composition
suggest 2 physical properties that could be measured + how
colour change of gases or solutions
- this could be done using a colorimeter calibrated with known concentrations of the coloured substance
release of gas
- this could be done with a gas syringe or by measuring loss of mass
what is the rate equation
rate = k[reactants]^order
what is the half life equation
k = ln(2) / half life
half life known as t 1/2
what is the arrhenius equation
k = Ae^(- Ea / R T)
rearranged to
lnk = -Ea / R T + lnA
what are all the variables in arrhenius equation
k = rate constant
A = pre exponential factor (aka arrhenius constant)
e = eulers constant
Ea = activation energy (Jmol-1)
T = temp (K)
R = gas constant
what 3 types of reactions does the arrhenius equation describe
- reactions involving gases
- reactions occurring in solution
- reactions occurring on the surface of a catalyst
mole fraction definition
the fraction of the total number of moles that each substance in a reaction is responsible for - the amount of moles of a component divided by total number of moles in the mixture
partial pressure definition
the proportion of the total pressure that each chemical in a reaction is responsible for - the amount of pressure that would be exerted by a gas within a mixture if it occupied the same volume on its own at the same temp
