When conc. `H_2SO_4` was added to an unknown salt present in a test tube, a brown gas (A) was evolved. The gas intensified when copper turnings were also added into this test tube. On cooling the gas A changed into a colourless gas (B). Write the equations for the reactions involved.

When conc. H_2SO_4 was added to an unknown salt present in a test tube, a brown gas (A) was evolved. The gas intensified when copper turnings were also added into this test tube. On cooling the gas A changed into a colourless gas (B). Identify the gases (A) and (B).

Which gas is evolved when concentrated HCl is added to powdered potassium dichromate. On passing the evolved gas through acidified KBr solution, the solution turns brown. Write the balanced equations for the reactions involved.

What happens when dil H_2SO_4 is added to a small amount of sodium carbonate taken in a test tube?

Four test tubed marked I,II,III and IV were taken 20 ml of Al_2(SO_4)_3 solution in water was poured in each of the test tube I, an iron nails was put in test tube II, copper turnings were put in test tube III and a clean aluminium strip was placed in test tube IV. No change was observed in any four any in the test tubes. the correct inference drawn is