Chapter 19, Problem 81E

Ethene (C₂H₄) can be halogenated by the reaction:

   ${\text{C}}_{\text{2}}{\text{H}}_{\text{4}}\left(g\right)+{\text{ X}}_{\text{2}}\left(g\right)\rightleftharpoons {\text{ C}}_{\text{2}}{\text{H}}_{\text{4}}{\text{X}}_{\text{2}}\left(g\right)$

Where X₂ can be Cl₂, Br₂, or I₂. Use the thermodynamic data given to calculate $\Delta H°$ , $\Delta S°$ , $\Delta G°$ and K_pfor the halogenation reaction by each of the three halogens at 25 ?C. Which reaction is most spontaneous? Least spontaneous?
What is the main factor responsible for the difference in the spontaneity of the three reactions? Does higher temperature make the reactions more spontaneous or less spontaneous?

Compound	$\Delta H_{\text{f}}^{°}(\text{kJ}/\text{mol)}$	$°(\text{J}/\text{mol}\cdot \text{K)}$
C2H4Cl2(g)	−129.7	308.0
C2H4Br2(g)	+38.3	330.6
C2H4I2(g)	+66.5	347.8