Chemical Reactions and Equations — Science STD 10 — Question

State two important uses of plaster of Paris.

What is meant by the ‘concentration of ore’?

When hydrogen burns in oxygen, water is formed and when water is electrolysed, then hydrogen and oxygen are produced. What type of reaction takes place:

1. In the first case?
2. In the second case?

Express the following facts in the form of a balanced chemical equation:

“When a strip of copper metal is placed in a solution of silver nitrate, metallic silver is precipitated and a solution containing copper nitrate is formed”.

What happens when a rod of zinc metal is dipped into a solution of copper sulphate? Give chemical equation of the reaction involved.

How are the following pairs related?
2, 2 - dimethylpropane and 2-methylbutane.

Explain why, the galvanised iron article is protected against rusting even if the zinc layer is broken.

Explain why:
Ionic compounds have generally high melting points.

A compound ‘X’ on heating with excess conc. sulphuric acid at 443K gives an unsaturated compound ‘Y’. ‘X’ also reacts with sodium metal to evolve a colourless gas ‘Z’. Identify ‘X’, ‘Y’ and ‘Z’. Write the equation of the chemical reaction of formation of ‘Y’ and also write the role of sulphuric acid in the reaction.

 Explain the following in terms of gain or loss of oxygen with one example:

1. Oxidation.
2. Reduction.