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# Equilibrium Temperatures

APCHEM-DQOLV3

Molecular iodine undergoes a process known as sublimation, in which it passes directly from solid to vapor without an intervening liquid state. The process can be described by the reaction:

$${ I }_{ 2 }(s)\rightleftharpoons { I }_{ 2 }(g)$$

Consider the following table showing the values of the enthalpy of formation, $\Delta { H }_{ formation }^{ \circ }$, and absolute entropy, ${ S }_{ formation }^{ \circ }$, for each of the two physical states of molecular iodine.

Thermodynamic Property ${I}_{2}(s)$ ${I}_{2}(g)$
$\Delta { H }_{ formation }$ $0$ $62\frac { \text{kJ} }{ \text{mol} }$
${ S }_{ formation }$ $116\frac { \text{J} }{ \text{ mol} \cdot \text{K} }$ $261\frac { \text{J} }{ \text{ mol}\cdot \text{K} }$

$\$

Using the data from the table, which of the following is the minimum temperature, in ºC, at which the sublimation of solid molecular iodine becomes spontaneous?

A

428ºC

B

155ºC

C

0.43ºC

D

2.3ºC