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Finding the order of reaction
The progress curve
A progress curve shows how the concentration of a reactant changes as the reaction proceeds.
The initial rate method
By drawing tangents at the origin of different progress curves
Once wehave the intial rates for different concentrations, we can find the order. If the graph of initial
rate against concentration is a straight line then the reaction is first order. If a graph of initial rate
against (conc)2 is straight then the reaction is second order.. if the rate doesn't change with
concentration it is zero order.
Using reciprocal of the reaction time as a measure of the rate
One way of measuring the initial rate of a reaction is to measure how long the reaction takes to
produce a small, fixed amount of one of the products the time taken is called the reaction time. If
the rate is high (the reaction proceeds quickly) then the reaction time will be large.
Rate = amount of iodine needed to obscure the cross/reaction time for sulphur to form.
The amount of iodine needed to obscure the cross will be the same of each experiment, so the rate
of reaction is proportional to the reciprocal of the reaction time for the cross to be obscured, 1/t
The shorted the time, the faster the reaction. If a graph of 1/t plotted against concentrations, a
straight line plot is obtained, showing that the rate of the reaction is proportional to the
Rate = k[a] to the power of x
Log rate = logk +xlog[a]
Gradienet = answer
Rate=k[a]to the power m[b]to the power n
2nd order = k[a]squared[b]