Final answer:
Heating wet sand before heating zinc granules is essential to dry the sand, ensuring it can effectively aid the thermal reaction in zinc processing. This preparation step mimics industrial conditions for reducing zinc oxide with carbon and prevents side reactions by removing moisture.
Step-by-step explanation:
It is necessary to heat wet sand before heating zinc granules to ensure that the sand is dry and can efficiently facilitate the thermal process needed in the subsequent chemical reaction involving zinc. When heating zinc sulfide or zinc granules, energy must be initially supplied to overcome the activation energy barrier depicted on the reaction coordinate diagram, allowing the reactants to reach a point where they can rapidly proceed to form the products while releasing energy in the form of heat, light, etc.
Zinc preparation involves heating zinc ores such as zinc sulfide to form zinc oxide, followed by a reduction process where carbon, often as coal, is used to reduce the zinc oxide to zinc vapor. The heating of wet sand helps to mimic these industrial conditions and ensures a controlled and efficient reaction when zinc granules are being processed in a smaller-scale laboratory setting.
Thus, the sand performs a vital role in the reaction by absorbing excess moisture and thereby influencing the temperature and rate of the thermally activated process. The absence of water also prevents any side reactions that could interfere with the intended chemical process of reducing zinc oxide.