# Equilibrium of NO₂ and N₂O₄

## Materials

• Two sealed NO₂ (gas) equilibrium tubes
• 4 liter beaker of ice water
• 4 liter beaker of hot water
• Hotplate

## Procedure

1. Place one tube in an ice bath and place a lid on top.
2. Use one tube as room temperature standard.
3. Place a third tube in a hot water bath and place a lid on top.
4. After a few minutes compare the color in the tubes.

Discussion:

Heat shifts the equilibrium in favor of NO₂ and the tube becomes darker. Since the formation of N₂O₄ is an exothermic reaction, lowering the temperature shifts the equilibrium in favor of colorless N₂O₄. In a dry ice - acetone bath, the N₂O₄ will crystallizes as a white solid.

$$\ce{ 2NO2 <=> N2O2 ~~~~ \Delta G_{rxn}^{{o}} = -2.8KJ/Mol }$$

 ΔHf (KJ/Mol) S (J/K*Mol) ΔGf (KJ/Mol) NO₂ 33.2 240.1 51.3 N₂O₄ 11.1 304.4 99.8