Which of the following is soluble in boiling water, but less soluble in cold water? — Qualitative and Quantitative Analysis Chemistry Question

💡 Solution & Explanation

Step 1: A green residue in the cobalt nitrate test indicates the presence of zinc (Zn2+) as it forms Rinmann's green. Step 2: On heating with concentrated H2SO4, nitrate salts release nitric acid, which decomposes to brown nitrogen dioxide (NO2) gas. Adding Cu turnings reduces the nitrate/nitric acid to liberate more brown NO2 gas vigorously. Step 3: Therefore, the white solid containing zinc and nitrate is zinc nitrate, Zn(NO3)2, matching option (a).