Equilibrium

If you have 5 mol of N2 and 6 mol of H2 reaching equilibrium, and 2.5 mol of HI forms; what is Kc?

I did 2.5/ 2 (because 1:2 ratio for both reactants and product) to get 1.25- I then subtracted this from 5 mol and 6 mol (all 1dm3) to get 3.75 and 4.75 respectively. I then worked out Kc to be 0.35 with no units.

Can someone tell me if this is right or not?

Hydrogen iodide formation is not possible if you start off with hydrogen and nitrogen ...

If you have 5 mol of N2 and 6 mol of H2 reaching equilibrium, and 2.5 mol of HI forms; what is Kc?

I did 2.5/ 2 (because 1:2 ratio for both reactants and product) to get 1.25- I then subtracted this from 5 mol and 6 mol (all 1dm3) to get 3.75 and 4.75 respectively. I then worked out Kc to be 0.35 with no units.

Can someone tell me if this is right or not?

It's correct...