[NewtoAtoms]

When 0.500 mol of N₂O₄ gas is placed in 2.50 L reaction vessel and heated to a set temperature, 65.3% of the N2O4 decomposes. Calculate K_c for the decomposition reaction

N₂O₄ (g) <----------> 2NO₂ (g)


Step #1      0.500 mol/2.50 L      0.2 M   
                      
                                 N₂O₄                     NO₂
Step #2      Initial         0.2 M                     O
              Change         0.1306 (65.3%)     34.70%
              Equilibrium      I AM STUCK HERE..

Step #3    kc = [NO₂]² / [N₂O₄] 

But I am so lost, what would the equilibrium value of NO₂ be??  0.347 or 34.7% of 0.2 M.

Can anyone help me with chem 12? I would be so grateful.

[Yggdrasil]

If you start with 0.2 M N₂O₄, and 0.1306M reacts, how much is left at equilibrium?

How much NO₂ is formed if 0.1306 M N₂O₄ reacts (hint: look at your balanced chemical equation)?

[NewtoAtoms]

If I start with 0.2M N2O4 and 65.3% decomposes (0.1306 M) there would be 0.0694 M remaining. 
Pardon my elementary questions, but I am trying to understand... but 0.0694 doesn't mean that the reaction is at equilibrium right?!?  It simply means there is 34.7% remaining.

If I were to refer back to the balanced chemical equation I could see that it has a ration of 1:2 therefore if 65.3% of N2O4 is decomposed, leaving 0.0694M, would it be correct to state that therefore 0.1388 M of NO2, would be created?

I am trying hard to grasp Chemistry, thank you very much for your patience and time.

[Yggdrasil]

If I start with 0.2M N2O4 and 65.3% decomposes (0.1306 M) there would be 0.0694 M remaining. 
Pardon my elementary questions, but I am trying to understand... but 0.0694 doesn't mean that the reaction is at equilibrium right?!?  It simply means there is 34.7% remaining.

From the way the problem is stated, I think you can take it to mean that when the reaction reaches equilibrium, 34.7% of the N2O4 remains.

If I were to refer back to the balanced chemical equation I could see that it has a ration of 1:2 therefore if 65.3% of N2O4 is decomposed, leaving 0.0694M, would it be correct to state that therefore 0.1388 M of NO2, would be created?

For every mole of N2O4 destroyed, you get two moles of NO2.

[NewtoAtoms]

If I start with 0.2M N2O4 and 65.3% decomposes (0.1306 M) there would be 0.0694 M remaining. 

Okay.. then for every mole of N2O4 destroyed I get 2 moles of No2, I would then say that at equilibrium (after 65.3% is decomposed) the resulting concentrations would be:

N2O4 = 0.0694M
NO2 = (0.1306 x 2) = 0.2612M

Would this be correct?

I am once again grateful for your *delete me*

[Yggdrasil]

N2O4 = 0.0694M
NO2 = (0.1306 x 2) = 0.2612M

Would this be correct?

This is correct.