Extraction of Zinc — Prelims Strategy

Prelims Strategy

To effectively tackle NEET questions on zinc extraction, a systematic approach is vital. Firstly, memorize the key ores of zinc (zinc blende, calamine) and their chemical formulas. Secondly, understand and memorize the sequence of steps: concentration (froth flotation for ZnS), conversion to oxide (roasting for ZnS, calcination for $ext{ZnCO}_3$), reduction (carbon reduction), and refining (fractional distillation, electrolytic refining).

For each step, learn the balanced chemical reactions and the specific conditions (e.g., temperature for roasting/reduction, presence/absence of air). Pay special attention to the thermodynamic principles, particularly how the Ellingham diagram explains the feasibility of carbon reduction for ZnO above $1000^circ\text{C}$.

For numerical problems, though less common in this specific topic, ensure you can apply basic stoichiometry to reaction equations. For conceptual questions, focus on the 'why' behind each step, such as why ZnS is roasted and not directly reduced, or why zinc is obtained as a vapor.

Be vigilant for trap options that confuse roasting with calcination, or misrepresent the electrode reactions in electrolytic refining. Practice identifying the correct reducing agent and understanding the role of zinc's low boiling point.

Regularly revise the reactions and conditions to ensure quick recall during the exam.