It is quire common for a solid to change from one structure to another at a temperature below its melting point. For example, sulfur undergoes a phase change from the rhombic crystal structure to the monoclinic crystal form at temperatures above $95 ^ { \circ } \mathrm { C }$. Which form of sulfur has the more ordered crystalline structure (has the smaller positional probability)?

It is quire common for a solid to change from one structure to another at a temperature below its melting point. For example, sulfur undergoes a phase change from the rhombic crystal structure to the monoclinic crystal form at temperatures above $95 ^ { \circ } \mathrm { C }$. Predict the signs of $\Delta H$ and $\Delta S$ for the process $S _ { \text { rhombic } } \longrightarrow S _ { \text { monoclinic } }$.

The major industrial use of hydrogen is in the production of ammonia by the Haber process:

$$3 \mathrm { H } _ { 2 } ( g ) + \mathrm { N } _ { 2 } ( g ) \longrightarrow 2 \mathrm { NH } _ { 3 } ( g )$$

At what temperatures is the reaction spontaneous at standard conditions? Assume that $\Delta H ^ { \circ }$ and $\Delta S ^ { \circ }$ do not depend on temperature.

Calculate the pH of the cathode compartment for the following reaction given $\mathscr { G } _ { cell } = 3.01 \mathrm { V }$ when $\left[ \mathrm { Cr } ^ { 3 + } \right] =$ $0.15\ M , \left[ \mathrm { Al } ^ { 3 + } \right] = 0.30\ \mathrm { M } ,$ and $\left[ \mathrm { Cr } _ { 2 } \mathrm { O } _ { 7 } ^ { 2 - } \right] = 0.55\ \mathrm { M }$.

$$2 \mathrm { Al } ( s ) + \mathrm { Cr } _ { 2 } \mathrm { O } _ { 7 } ^ { 2 - } ( a q ) + 14 \mathrm { H } ^ { + } ( a q ) \longrightarrow 2 \mathrm { Al } ^ { 3 + } ( a q ) + 2 \mathrm { Cr } ^ { 3 + } ( a q ) + 7 \mathrm { H } _ { 2 } \mathrm { O } ( l )$$

Water in a crystal that is an integral part of the crystal structure is called ______.