Chemistry
posted by Jefferson .
At equilibrium, the concentrations in this system were found to be [N2]=[O2]=0.100 M and [NO]=0.400 M.
N2 (g) + O2 (g) > 2NO (g)
If more NO is added, bringing its concentration to 0.700 M, what will the final concentration of NO be after equilibrium is reestablished?

...........N2 + O2 ==> 2NO
E.........0.1....0.1....0.4
add 0.3.................0.7
new I.....0.1....0.1....0.7
C..........+x......+x....2x
new E....0.1+x..0.1+x...0.72x
Use the first E line to calculate Kc. Substitute the equilibrium conditions and solve for kc.
Then substitute the NEW E line into the Kc expression and solve for x, 0.1_x and 0.72x
Post your work if you get stuck. 
got it!! the answer is 0.6 and it was correct!! Thank you so so much!!