A metal compound A reacts with dilute hydrochloric acid to produce effervescence. The gas evolved extinguishes a burning candle.

Name the gas that extinguishes the burning candle.

${\mathrm{Fe}}_2{\mathrm{O}}_3+2\mathrm{Al}\to {\mathrm{Al}}_2{\mathrm{O}}_3+2\mathrm{Fe}$

The above reaction is an example of a 

Translate the following statement into a chemical equation and then balance it. 

Hydrogen gas combines with nitrogen to form ammonia.

Translate the following statement into a chemical equation and then balance it. 

Hydrogen sulphide gas burns in the air to give water and sulphur dioxide. 

What does one mean by exothermic and endothermic reactions? Give examples. 

Oil and fat containing food items are flushed with nitrogen. Why? 

What would you observe when zinc is added to a solution of iron($\mathrm{II}$) sulphate? Write the chemical reaction that takes place.