```![enter image description here][1]

Figure. A schematic diagram showing the effect of the temperature on the stability of an enzyme catalysed reaction. The curves show the percentage activity remaining as the incubation period increases. From the top they represent equal increases in the incubation temperature (50º C, 55º C, 60º C, 65º C and 70º C).

The ![enter image description here][2] is a unitless number, that summarizes the effect of raising temperature 10º C on the rate of a chemical reaction. A ![enter image description here][3] of 2.0 suggests that raising the temperature of a system by 10º C will effectively double the rate of the reaction. This value would be expected for most chemical reactions occurring within normal physiological temperatures.

Mathematically, ![enter image description here][4] can be represented by the following expression:

![enter image description here][5]

where

t2 = higher temperature    k2 = rate at t2
t1 = lower temperature     k1 = rate at t1

Ussualy the temperature difference is about 10º C, then you can simplify the equation

![enter image description here][6]

Edit: You can easly calculate k form Arrhenius equation ![enter image description here][7]

where k is the kinetic rate constant for the reaction, A is the Arrhenius constant, also known as the frequency factor, ![enter image description here][8] is the standard free energy of activation (kJ M-1) which depends on entropic and enthalpic factors, R is the gas law constant and T is the absolute temperature.

[1]: http://i.stack.imgur.com/qqVuB.gif
[2]: http://i.stack.imgur.com/Apbvg.gif
[3]: http://i.stack.imgur.com/Apbvg.gif
[4]: http://i.stack.imgur.com/Apbvg.gif
[5]: http://i.stack.imgur.com/THkdC.gif
[6]: http://i.stack.imgur.com/8PkD6.gif
[7]: http://i.stack.imgur.com/kWi4v.gif
[8]: http://i.stack.imgur.com/XooTu.gif```