module 3+5: rates of reaction
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what is the order in respect to the reactant when: reactant concentration doubles and rate stays the same
order 0
what is the order in respect to the reactant when: reactant concentration doubles and rate doubles
order 1
what is the order in respect to the reactant when: reactant concentration doubles and rate quadruples
order 2
how do you calculate the overall order
find the sum of the reactant’s orders
what equation is used with orders and the rate constant
.
how do you find the units for K
rate is: mol/dm³/s sub into an eq. and cancel out values to find thge units of k
what does this concentration-time graph show?
0 order
what does this concentration-time graph show?
1 order
how can you calculate the order of a reaction using half lives
zero order: successive half lives decrease with time first order: half life remains constant second order: successive half lives increase with time
what order does this rate-concentration graph show
order 0
what order does this rate-concentration graph show
first order
what order does this rate-concentration graph show
second order
what is the rate-determining step
the step that determines the rate of the reaction, the slowest step all reactants from the rate equation will appear in the rate-determining step
what is the d-block
elements whose highest occupied energy level is a d sub-shell
what are the elements of the arrhenius equation and units
.
how does pressure influence rate of reaction
higher pressures compress gases into a smaller volume, thus increasing concentration so that collisions are at a higher frequency because there are more particles per unit area
how does surface area impact rate of reaction
grinding a solid increases the SA/V ratio, so the frequency of collisions increases as there are more surfaces for collisions to occur
how do catalysts affect reaction rate
they increase it without being used up they may react to form an intermediate but are then regenerated they lower activation energy through providing an alternate reaction pathway
describe the Boltzmann distribution curve and how it changes with temperature and catalysts
line starts at 0 bc no molecules have 0 energy line never again meets the x axis bc there’s no max energy the area under the curve = total no. of particles
define homogeneous catalysts
the catalysts and reactants are in the same physical state, usually both aqueous
define heterogeneous catalysts
the catalyst and reactants are different physical states, usually where reactants are gases but the catalyst is a solid
what are economic and sustainability advantages of catalysts
• using a catalyst can mean lower temps and pressures can be used, saving energy costs • saving energy costs means less us of fossil fuels/electricity which means less CO2 emissions • catalysts can enable reactions to be used which have better atom economies
what is a half life
how long it takes for half of a reactant to be used up
why is it unlikely for some reactions to take place in one step
• a collision is unlikely between more than 2 species • the stoichiometry in the rate equation doesn’t match the overall equation