If two salts are heated strongly in two different dry test tube then brown fumes of NO2 will be found to evolve from the test tube containing Ca(NO3)2 (*) whereas colorless gas will come out from other test tube containing NaNO3. This colorless gas supports combustion and it can be confirmed that the gas is O2 by other confirmatory test like its absorption in alkaline pyrogallol,
equations
2Ca(NO3)2()→ 2CaO() +2NO2(g)+O2(g)
2Na(NO3)()→ 2NaNO2() +O2(g)
