## How do you calculate activation energy per vacancy?

the question is like this:
Calculate the activation energy needed to create a single vacancy in aluminium, given:
T= 500 Celsius
Density (500 Celsius) = 2.62 gr/cm3
n = 7.57e23 m-3
Mw (Al) = 26.98 gr/mol

I know these Formulas:
n = N*exp (Q/kT) (k = boltzmann's constant)
N = Na*Density/Mw (Na = avogardo's number)
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 Blog Entries: 2 Hey ENgez, welcome to PF It seems like a direct question with a direct answer, just find Q [the activation energy required to create one vacancy].
 I did Find Q and it turned out to be 1.053 ev/mole or 16.85e-20 Joule/mole, but according to the answer sheet its supposed to be 72.33 kJoule/mole. Is it possible for the answer to be so big or is there a mistake in the sheet? And if there isn't, what am i doing wrong? Btw, thanks drizzle :)