How to find Kc whenvalue of Kp is given

 

Please Check: 
Calculate the equilibrium concentrations of each species for the following reaction at 298 K.  The initial 
concentration of each species is 1.00 M.  The Kp for the reaction is 3.63 x10-4. 
 
PCl5(g) ⇌ PCl3(g) + Cl2(g
 
First the teacher stated I need to convert Kp to Kc: 
Kp=Kc(RT)^n
moles of products minus moles of reactants = 1
3.63x10^-4 = Kc(0.082058)(298)^1
 
when I do this i get Kc=1.48X10^-5 , and my teacher said go back and check my calculation, can someone explain what my calucaltion error is? 
 
 
 
thanks 

The other way to convert the two equilibrium constants is Kc = K(RT)

 

Plug in your values again and you should get the answer you are looking for.

 

This site should help you through things: 

http://chemwiki.ucdavis.edu/index.php?title=Physical_Chemistry/Chemical_...