(a) The blue colour of crystals of a substance changed on heating in a closed test tube but the colour was regained after sometime on cooling. Name the substance and write irts chemical formula. Explain the phenomenon invilved.
(b) Write name and chemical formula of two such compounds whose one formula unit is associated with 10 and 2 water molecules respectively.

A metal 'P' when exposed to moist air for longer period of times, loses its shining brown surface and gains green coating, what has happened ? Identify the metal, write the name and chemical formula of green coloured compound. List two ways to prevent this process.

(a) What is the colour of ferrous sulphate crystals ? How does this colour change after heating ? (b) Name the products formed on strongly heating ferrous sulphate crystals. What type of chemical reaction occurs in this change ? Write chemical equation of the reaction.

When water is added gradually to a white solid X, a hissing sound is heard and a lot of heat is produced forming a product Y.A suspension of Y in water is applies to the walls of a house during white washing. A clear solution of Y is also used for testing carbon dioxide gas in the laboratory. (a) What could be solid X? Write its chemical formula. (b) What could be product Y ? Write its chemical formula. (c ) What is the common name of the solution of Y which is used for testing carbon dioxide gas? (d) Write chemical equation of the reaction which takes place on adding water to solid X. (e) Which characteristic of chemical reactions is illustrated by this example ?

2g of ferrous sulphate crystals are heated in a boiling tube. (i) State the colour of ferrous sulphate crystals both before heating and after heating. (ii) Name the gases produced during heating. (iii) Write the chemical equation for the reaction.

When a blue coloured copper salt is heated strongly, it forms a white copper salt. The white copper salt can be reconverted into blue salt by adding a liquid X. (a) Write the formula of blue copper salt. (b) Write the formula of white copper salt. (c) What substance is lost when blue copper salt is converted into white copper salt? (d) Name the liquid X.

An organic compound C_(2)H_(4)O_(2) is taken in a test-tube and a pinch of baking soda is added to it. A gas it evolved which turns lime water milky. (a) Name the gas evolved. (b) Name the functional group present in the organic compound. (c) Write the name and formula of the organic compound.