what is the effect of temperature Change on the following equilibrium. 2NO2 arrow mark N2O4. delta h =-57.8
Answers
Explanation:
The Effect of Temperature on the NO2/N2O4 Equilibrium
Chemical Concept Demonstrated: Temperature's effect on equilibrium
Demonstration:
Four glass tubes are sealed with NO2 gas.
The first tube is placed in a hot water bath.
The second is placed in ice-water.
The third is placed in a flask filled with dry-ice/acetone slush.
The fourth is placed in liquid nitrogen.
Compare the glass tubes.
Observations:
NO2 is brown and N2O4 is colorless. The intensity of the brown color decreases as the temperature decreases. Therefore, a decrease in temperature yields and increase in N2O4. Equilibrium is shifted to the N2O4 side upon a decrease in temperature.
Explanation (including important chemical equations):
2 NO2 (g) <=> N2O4 (g)
The standard enthalpy (delta H� = -57.2 kJ) and the entropy (delta S� = -175.83 kJ) of reaction can be calculated from the follow standard-state enthalpies of formation and standard-state entropies.
Compound delta H�f (kJ/mol) delta S� (J/mol-K)
NO2 33.18 240.06
N2O4 9.16 304.29
We can then invoke the assumption that the temperature dependence of delta H� for this reaction is small to estimate the equilibrium constant at various temperatures.
Temperature delta G� (kJ) Kp
100 �C 8.4 0.066
0 �C -9.2 58
-78 �C -22.9 1.3 x 106
-196 �C -43.6 3.7 x 1029
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