The function of fluorspar in the electrolytic reduction of alumina dissolved in fused cryolite (Na3A — Metallurgy and Isolation of Elements Chemistry Question

💡 Solution & Explanation

Step 1: Pure alumina (Al2O3) has an exceptionally high melting point (above 2000°C) and is a very poor conductor of electricity, making its direct electrolysis practically impossible. Step 2: To overcome this, alumina is dissolved in a molten bath of cryolite (Na3AlF6) and fluorspar (CaF2). Step 3: The addition of fluorspar (CaF2) and cryolite lowers the melting temperature of the mixture to around 950°C and significantly increases the electrical conductivity of the fused electrolyte, which corresponds to option (b).