Which of the following salt gives green colour mass in cobalt nitrate charcoal cavity test? — Qualitative and Quantitative Analysis Chemistry Question

💡 Solution & Explanation

Step 1: The cobalt nitrate test is used to identify certain metal ions (like Zn2+, Al3+, Mg2+) that form characteristic colored mixed oxides upon heating on a charcoal block with cobalt nitrate. Step 2: Zinc salts react with cobalt nitrate to form cobalt zincate, CoZnO2, which has a characteristic green color. Step 3: This green mass is historically known as Rinmann's green. Hence, zinc salts give a green color, which corresponds to option (a).