16.2 Activation Energy

What does this mean?

We should know that for a reaction to happen molecules must

a) C_____________________

b) With enough E_______________

c) And in the correct O________________

So any attempt to calculate the rate equation must include all these factors.

k = p x Z x e^(-Ea/RT)

p = Steric Factor (Fraction of collisions with correct orientation)

Z = Collision Number (Collision Frequency Constant)

(-Ea/RT) represents the fraction of molecules with enough energy - Exponential Factor

p and Z are not temperature dependent so the Arrhenius Equation is usually used as

k = A e^(-Ea/RT)

So in this case A (the pre-exponential factor) takes the place of both.

And is more commonly used as;

lnk = lnA - (Ea/RT)

Or

lnk = - (Ea/RT) + lnA

You should know the Maths expression for a straight line Y = mX + c

Where m = ________________________

& c = _____________________________

If we plotted a graph of ln k vs 1/T

Use the Graph below to estimate k and Ea

Use the Graph below to make a rough estimate k and Ea