Rates of reaction
No description yet. This curated deck is ready for daily study.
Card preview (24)
how do you calculate rate from concentration?
change in concentration/ time
what is the units for rate?
moldm-3s-1
describe a zero order reaction
-concentration of reactant has no effect on the rate, the reaction is zero order with respect to the reactant -any number raised to the power of zero is one -concentration does not affect the rate
describe the first order of reaction
-a reaction is first order with respect to the reactant when the rate depends on its concentration raised to the power of one -e.g if the conc of reactant is doubled the rate will double
Describe second order reaction
-a reaction is second order with respect to a reactant when the rate depends on its concentration raised to the power of two -e.g if the conc of reactant is doubled, the rate increases by four
what is the rate equation?
rate= k [A] to the power of m [B] to the power of n
what is the rate constant?
the proportionality constant, number that mathematically converts between the rate of reaction and concentrations and orders.
what is the overall order and how is it calculated?
-overall order of reaction gives the overall effect of the concentrations of all reactants on the rate of reaction. -overall order= sum of orders with respect to reactants
what is the units for k in an overall reaction order of zero?
moldm-3s-1
what is the units for k in an overall reaction order of two?
dm3mol-1s-1
how do you continuously monitor the rate of reactants producing gases?
-monitor by gas collection -monitor by mass loss
how do you monitor the rate of reactants forming a colour change?
colorimeter
how does a colorimeter work?
wavelength of light passing through a coloured solution is controlled using a filter. The amount of light absorbed by a solution is measured.
how do you calculate the rate of reaction from a concentration/ time graph?
calculate the gradient
what does a zero, first and second order look like on a concentration/ time graph?
-zero order: straight line with a negative gradient- the gradient is equal to the rate constant -first order: downward curve with decreasing gradient- the rate constant can be determined using half life -second order: also downward curve with steeper curve but trailing off more slowly
what is half life, t1/2?
time taken for half of a reactant to be used up
Describe half life and first order reactions?
first order reactions have a constant half life with the concentration halving every half life- exponential decay. If the successive half-lives are the same, the reaction is first order with respect to the reactant.
Describe the rate/ concentration graphs of a zero order reaction
1)zero order: -intercept on the y-axis gives the rate constant, k -horizontal straight line with zero gradient
Describe the rate/ concentration graphs of a first order reaction
First order: -produces a straight line graph through origin -rate is directly proportional to concentration -rate constant determined by measuring the gradient
Describe the rate/ concentration graphs of a second order reaction
-produces upward curve with increasing gradient -rate constant cannot be determined from this as its a curve -by plotting a second graph of the rate against the concentration squared, the result is a straight line through the origin. The gradient of this straight line is equal to the rate constant, k.
how do you calculate rate constant from half-life?
k=In2/t1/2
how do you calculate initial rate from a graph?
extrapolate the graph, tangent and measure the gradient
what is initial rate proportional to?
1/t
what is the iodine clock experiment and its equation?
A reaction where you can time how long it takes for a colour change too occur H2O2(aq) + 2H+(aq) + 2I-(aq) -> 2H2O(l) + I2(aq)