Final answer:
To separate zinc from brass, distillation is used based on the different boiling points of zinc and other metals. Redistillation and refining, which may involve electrolysis, further purify the zinc. Another method involves dissolving zinc in hydrochloric acid while leaving other metals intact.
Step-by-step explanation:
To separate zinc from brass, which is an alloy of copper and zinc, various steps involving physical and chemical processes are required. One common method is the use of distillation due to the different boiling points of the constituent metals. The process involves heating the brass to a temperature where zinc becomes a vapor (boiling point 907 °C) while the other metals remain solid or liquid. Impurities such as cadmium, iron, lead, and arsenic also have different boiling points and can be separated during careful redistillation. Additionally, refining might be required as the final step, where methods like electrolysis could be employed. For instance, in the preparation of zinc from its ores, carbon can reduce zinc oxide to form zinc vapor, which is then condensed to pure zinc.
Zinc is also known to be an active metal that readily dissolves in hydrochloric acid, resulting in a solution of zinc ions (Zn²+), chloride ions (Cl-), and hydrogen gas. This principle can also be utilized for the separation process, where zinc parts of brass can be dissolved and potentially recovered from solution after copper parts remain unaffected.