The nitrate salt which does not give a mixture of NO₂ and O₂ on heating is:

1. AgNO₃
2. KNO₃
3. Cu(NO₃)₂
4. Zn(NO₃)₂

The chemical used in the brown ring test is:

1. CuSO₄
2. FeSO₄
3. Fe₂(SO₄)₃
4. ZnSO₄

In the laboratory preparation of nitric acid, nitre is heated with :

1. conc. HCl
2. conc. H₂SO₄
3. dil. H₂SO₄
4. conc. H₃PO₄

Nitric acid is manufactured by :

1. Bayer's process
2. Haber's process
3. Ostwald process
4. Contact process