Question

l. Give
one
example each

of a
chemical reactions
characterised by
i) Evolution
of gas
17 Change
in
colour​

Answer 1

Answer:

1) evolution of gas---›Some chemical reactions take place with the evolution of gas. For example, when zinc reacts with hydrochloric acid, hydrogen gas is evolved with formation of zinc chloride. ... For example, barium chloride reacts with sodium sulphate and forms sodium chloride and precipitate of barium sulfate.

2) change in colour---›Copper reacts with oxygen, H2O and CO2 to give copper carbonate, which changes color from brown to blue or blue green. Rusting, blackening of surfaces of cut vegetables and fruits are other examples of change of color in a chemical reaction