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

Cold and dilute HNO₃ reacts with Cu to give :

1. NO₂
2. NO
3. N₂
4. O₂

The brown ring test is used for the detection of :

1. CO₃^2-
2. Cl^-
3. NO₃^-
4. SO₃^2-