Do you need to know A to use the Arrhenius equation?

k = Ae^–E_a/RT

Using the exponential form of the Arrhenius equation,

rate constants measured at different temperatures can be used

to determine E_aand A graphically and then<
to use A to calculate the rate constant at a different temperature

A form of the Arrhenius equation in which A does not appear can be derived by taking the difference between the logarithmic form at two different temperatures.

ln k₂	=	-	E_a	×	1	+ ln A
			R		T₂

minus

ln k₁	=	-	E_a	×	1	+ ln A
			R		T₁

equals

ln	k₂	=	-	E_a	(	1	-	1	)
	k₁			R		T₂		T₁

This relationship is a convenient way

to calculate E_a from k at two different temperatures
to determine k at a second temperature from k at one temperature and E_a