Equilibrium Constant Calculation

[Spallation]

Determine the equilibrium constant, my working is below:

Equilibrium reaction:
[PLAIN]http://img34.imageshack.us/img34/5106/reactiondy.jpg

At 730 oC the equilibrium concentrations of reactants and products are:

[H2 (g) ] / mol dm-3 : 2.40 x 10-7

[Cl2 (g)] / mol dm-3 : 2.40 x 10-7

[HCl (g)] / mol dm-3: 5.37 x 10-3

[PLAIN]http://img163.imageshack.us/img163/4485/equationconstant.jpg




My answer is wrong but I don't know why, I must have missed something out. Thanks for any explanations I receive.

 

[tiny-tim]

Welcome to PF!

Hi Spallation! Welcome to PF!

Your arithmetic is wrong … how did you get 2.9 10^-5 ?

 

[Spallation]

I rounded to two significant figures and put it in scientific notation from the answer 0.000028836

Thanks for the welcome :)

 

[tiny-tim]

erm … 0.000028836 is just the top line!

 

[Spallation]

Woah so it is, what a mistake to make, my new answer is 500640625.

 

[Studiot]

I agree with Tiny Tim your arithmetic is 13 orders of magnitude adrift. This is more than a rounding error.

 

[tiny-tim]

Woah so it is, what a mistake to make, my new answer is 500640625.

Woohoo! ​

(and you were only out originally by about 10¹⁴ ! )

 

[Spallation]

Indeed, how embarrasing! Thank you for the help.