Explain why aluminum cannot be extracted from aluminum oxide by heating with carbon...
Check the final answer first, then review the worked steps.
Problem
Explain why aluminum cannot be extracted from aluminum oxide by heating with carbon, given that lead can be extracted from lead oxide by heating with carbon.
Answer
Aluminum is more reactive than carbon, so carbon cannot displace aluminum from aluminum oxide. Lead is less reactive than carbon, so carbon can displace lead from lead oxide.
Step-by-step solution
1. Understand the principle of extraction using carbon: The extraction of a metal from its oxide using carbon relies on the principle that carbon can act as a reducing agent. This is possible if the metal is less reactive than carbon. In such cases, carbon will displace the metal from its oxide at high temperatures. For example, lead oxide can be heated with carbon to produce lead and carbon monoxide: $PbO(s) + C(s)
ightarrow Pb(l) + CO(g)$.
2. Consider the reactivity of aluminum: Aluminum is a highly reactive metal. Its position in the reactivity series is significantly above carbon. This means that aluminum has a stronger tendency to bond with oxygen than carbon does.
3. Explain why carbon cannot extract aluminum: Because aluminum is more reactive than carbon, carbon cannot displace aluminum from aluminum oxide ($Al_2O_3$). The reaction would require carbon to remove oxygen from aluminum, but aluminum has a greater affinity for oxygen. Therefore, heating aluminum oxide with carbon will not result in the extraction of aluminum.
4. Contrast with lead extraction: Lead is less reactive than carbon. This is why carbon can successfully reduce lead oxide to extract lead. The difference in reactivity between aluminum and lead with respect to carbon is the key factor.