Chemistry Forums for Students > Chemistry Olympiad and other competitions

NO2 problem

**oque**:

Nitrogen dioxide NO2 is one of a number of oxides of nitrogen found in our atmosphere. It

can dimerize to give N2O4 (g):

2NO2 (g) ::equil:: N 2 O 4 (g)

At 298 K, the ∆G of formation for N2O4 (g) is 98.28 kJ, whereas for NO2 (g) is 51.84

kJ. Starting with one mole of N2O4 (g) at 1.0 atm and 298 K, calculate what fraction

will be decomposed if the total pressure is kept constant at 1.0 atm and the

temperature is maintained at 298 K.

Supposedly the answer is 0.166, but I haven't been able to find the way to solve it correctly, my result was 0.39.

I calculated the constant K with ΔG= -RTlnK. The ΔG for the whole reaction is (according to me) 5.4kJ

The constant I calculated is 0.99782. Then:

(NO2)2/(N2O4)

(2x)2/(1-x)= K

Solve the cuadratic ecuation and it's 0.39, Where did I go wrong?

**Borek**:

--- Quote from: oque on May 01, 2019, 03:54:51 PM ---The ΔG for the whole reaction is (according to me) 5.4kJ

The constant I calculated is 0.99782.

--- End quote ---

Check this part.

**oque**:

I calculated again and its 0.113. I realized that ΔG it's in kJ, not in J in order to use R.

But again, now I solved the quadratic equation and its 0.15468 not close enough to the right answer.

**mjc123**:

I agree with you, but you get the given answer if K = 0.133. Perhaps the book made a transcription error in doing the quadratic equation.

**AWK**:

The problem comes from ICHO24 and its solution is given

https://www.alquimicos.com/oq_reg/internacionales/icho_24.pdf

Navigation

[0] Message Index

[#] Next page

Go to full version