Most representative metals are too reactive to occur as free elements in nature. Instead, they are found in minerals and other compounds. This lesson introduces where important representative metals occur and explains how electrolysis is used to isolate sodium, aluminum, and magnesium.
Representative metals are commonly found as ions in minerals, rather than as pure elements. Their ores provide the compounds from which metals can be extracted.
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What is electrolysis?
Electrolysis uses electrical energy to drive an unfavorable chemical reaction, including the reduction of reactive metal ions to metals.
What are the products of sodium chloride electrolysis in a Downs cell?
Molten sodium forms at the cathode and chlorine gas forms at the anode: 2NaCl(l)→2Na(l)+Cl2(g).
How does a Downs cell keep sodium and chlorine from recombining?
The products are separated: less-dense liquid sodium rises into a collector, while chlorine gas is directed to storage.
What is the purpose of cryolite in aluminum production?
Aluminum oxide dissolves in molten cryolite, with calcium fluoride also present, so the mixture can be electrolyzed at a lower temperature.
How is magnesium chloride prepared from seawater for electrolysis?
Calcium hydroxide precipitates magnesium hydroxide from seawater; hydrochloric acid converts it to magnesium chloride, which is recovered and melted for electrolysis.
Quiz questions
Why are most representative metals not found as free elements in nature?Answer: They are reactive and usually occur combined in compounds and minerals.
What forms when zinc sulfide ore is roasted in air?Answer: Zinc oxide and sulfur dioxide form.
Why is calcium chloride added to sodium chloride in a Downs cell?Answer: It lowers the electrolyte's melting point to about 600 °C.
Which sequence describes the main purification steps before aluminum oxide is electrolyzed?Answer: Treat bauxite with hot sodium hydroxide, filter impurities, precipitate aluminum hydroxide, then heat it to form aluminum oxide.
What distinguishes chemical reduction from electrolysis in metal production?Answer: Chemical reduction uses a reducing agent and is often less expensive when practical.
Based on Chemistry 2e by Paul Flowers, Klaus Theopold, Richard Langley, William R. Robinson, PhD (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.