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describe the iodine clock experiment
H2O + 2H+ + 2I——- 2H2O
add sodium thiosulfate and starch (acts as an indicator) to excess hydrogen peroxide
sodium thiosulfate reacts immediately
when no sodium thiosulfate is left to react it then reacts with starch which gives a deep blue colour
what is the rate equation
rate is k(A)^(B)^b
rate is in moldm-3s-1
small numbers are orders of the reaction
big letters are conc of substance
what does zero order mean
changes in the concentration has no effect on rate
what does 1st order mean
changes in concentration has a proportional effect on rate
what does 2nd order mean
changes in conc has a squared proportional effect (if conc doubles then rate quadruples)
draw a first order rate concentration graph and a concentration time graph
draw zero order rate concentration graphs and concentration time graphs
draw a 2nd order rate concentration graph and concentration time graph
what is half life
the time taken for half of the reactant to be used up
half life is independent of conc. so each half life will be ______
the same length
what calculation uses half life to calculate rate
k= ln2/t^1/2 units= s^-1
what is the rate determining step
the slowest step in a multi-step reaction, determines the whole reaction rate
label Arrhenius equation
k=rate constant
A= Arrhenius constant
e= exponential
-Ea= activation energy (j)
R= gas constant 8.314
T= temperature in kelvin
what does Arrhenius equation link
activation energy and temperature to the rate constant
