(i) Define a double displacement reaction.
(ii) Write the chemical equation of a double displacement reaction which is also a 
(a) Neutralisation reaction
(b) Precipitation reaction. Give justification of your answer.

Equal length of magnesium ribbon are taken in two test tubes W. and 'B', H₂SO₄ is added to test tube 'A '. and H₂CO₃ in the test tube 'B' in equal amounts:
(a) Identify the test tube showing vigorous reaction.
(b) Give reason to support your answer.
(c) Name the gas liberated in both the tubes. How will you prove its liberation?
(d) Write chemical 'equations for both reactions.
(e) Out of the two acids taken above
(i) which one will have lower pH value.
(ii) lower H⁺ concentration respectively.

What happens when:
(i) Dilute hydrochloric acid is added to solid sodium carbonate.
(ii) Quicklime is treated with water.
(iii) Sodium chloride solution is added to lead nitrate solution.
Also write the chemical equation in each case.

Name the three products of 'chlor-alkali' process. Write one commercially or industrially important material each that can be prepared from each of these products

(i) Write the chemical formula of each of the following:
(a) Plaster of Paris
(b) Gypsum.
(ii) How can plaster of paris be converted into gypsum?
(iii) List anyone use of plaster of paris.

In the following schematic diagram for the preparation of hydrogen gas as shown in the figure, what would happen if following changes are made?

(i) In place of zinc granules, the same amount of zinc dust is taken in the test-tube.
(ii) Instead of dilute sulphuric acid, dilute hydrochloric acid is taken.
(iii) Sodium hydroxide is taken in place of dilute sulphuric acid and the test-tube is heated.

Explain the action of dilute hydrochloric acid on the following with chemical equation:
(i) magnesium ribbon
(ii) sodium hydroxide
(iii) crushed egg shells

(i) A white powder is an active ingredient of antacids and is used in preparation of baking powder. Name the compound and explain that how it is manufactured. Give chemical equation.
(ii) Write a chemical equation to show the effect of heat on this compound.

A sanitary worker uses a white chemical having strong smell of chlorine gas to disinfect the water tank.
(i) Identify the chemical compound, write its chemical formula.
(ii) Give chemical equation for its preparation.
(iii) Write its two uses other than disinfection.

A liquid has a pH less than 7 which represent all acidic solution:
(i) State the nature of the solution, if its pH increases from 7 to 14.
(ii) Mention the ion whose concentration increases with the increase in pH value.
(iii) Suggest a method that is generally used for measuring the pH value.