Problem 93 - Chemistry: The Central Science

Question

Ultrapure germanium, like silicon, is used in semiconductors. Germanium of "ordinary" purity is prepared by the high-temperature reduction of \(\mathrm{GeO}_{2}\) with carbon. The Ge is converted to \(\mathrm{GeCl}_{4}\) by treatment with \(\mathrm{Cl}_{2}\) and then purified by distillation; \(\mathrm{GeCl}_{4}\) is then hydrolyzed in water to \(\mathrm{GeO}_{2}\) and reduced to the elemental form with \(\mathrm{H}_{2}\). The element is then zone refined. Write a balanced chemical equation for each of the chemical transformations in the course of forming ultrapure Ge from \(\mathrm{GeO}_{2}\).

Step-by-Step Solution

Answer

The balanced chemical equations for the chemical transformations involved in converting \(\mathrm{GeO}_{2}\) to ultrapure germanium are as follows: 1. \(\mathrm{GeO}_{2} + 2 \mathrm{C} \rightarrow \mathrm{Ge} + 2 \mathrm{CO}_{2}\) 2. \(\mathrm{Ge} + 4 \mathrm{Cl}_{2} \rightarrow \mathrm{GeCl}_{4}\) 3. \(\mathrm{GeCl}_{4} + 2 \mathrm{H}_{2}\mathrm{O} \rightarrow \mathrm{GeO}_{2} + 4 \mathrm{HCl}\) 4. \(\mathrm{GeO}_{2} + 2 \mathrm{H}_{2} \rightarrow \mathrm{Ge} + 2 \mathrm{H}_{2}\mathrm{O}\)

Step 1: Reduction of \(\mathrm{GeO}_{2}\) with carbon

In this step, \(\mathrm{GeO}_{2}\) reacts with carbon (C) to form germanium (Ge) and carbon dioxide (\(\mathrm{CO}_{2}\)). To balance the equation, we must ensure that the number of atoms of each element is the same on both sides of the equation. The balanced equation is: \[\mathrm{GeO}_{2} + 2 \mathrm{C} \rightarrow \mathrm{Ge} + 2 \mathrm{CO}_{2}\]

Step 2: Conversion of Ge to \(\mathrm{GeCl}_{4}\) with \(\mathrm{Cl}_{2}\)

In this step, germanium (Ge) reacts with chlorine gas (\(\mathrm{Cl}_{2}\)) to form germanium tetrachloride (\(\mathrm{GeCl}_{4}\)). The balanced equation for this step is: \[\mathrm{Ge} + 4 \mathrm{Cl}_{2} \rightarrow \mathrm{GeCl}_{4}\]

Step 4: Hydrolysis of \(\mathrm{GeCl}_{4}\) in water

In this step, germanium tetrachloride (\(\mathrm{GeCl}_{4}\)) reacts with water (\(\mathrm{H}_{2}\mathrm{O}\)) to form germanium dioxide (\(\mathrm{GeO}_{2}\)) and hydrochloric acid (\(\mathrm{HCl}\)). The balanced equation for this step is: \[\mathrm{GeCl}_{4} + 2 \mathrm{H}_{2}\mathrm{O} \rightarrow \mathrm{GeO}_{2} + 4 \mathrm{HCl}\]

Step 5: Reduction of \(\mathrm{GeO}_{2}\) with \(\mathrm{H}_{2}\)

In this step, germanium dioxide (\(\mathrm{GeO}_{2}\)) reacts with hydrogen gas (\(\mathrm{H}_{2}\)) to form germanium (Ge) and water (\(\mathrm{H}_{2}\mathrm{O}\)). The balanced equation is: \[\mathrm{GeO}_{2} + 2 \mathrm{H}_{2} \rightarrow \mathrm{Ge} + 2 \mathrm{H}_{2}\mathrm{O}\] These are the balanced chemical equations for the chemical transformations involved in converting \(\mathrm{GeO}_{2}\) to ultrapure Ge.