Question

Which of the following is an exothermic reaction?

Answer 1

Chemical reactions can be broadly classified into two categories from the context of heat requirement. These include; endothermic and exothermic reactions.

Endothermic reactions proceed with the absorption of heat while exothermic reactions are accompanied by the evolution of heat.

1) Oxidation of iron involves reaction of elemental iron with oxygen to form iron oxide (rust). This is essentially a corrosion reaction in which the metallic bonds in Fe are broken and new bonds between Fe and O are formed, This is an exothermic reaction

4Fe + 3O2 → 2Fe2O3

Ans D)

2) The process of condensation i.e. phase change liquid to solid (or gas to liquid) involves release of heat to the surroundings, hence it will be an exothermic reaction.

Ans B)

3) Specific heat is the amount of heat required to raise the temperature of 1 g of a substance by a 1 C. Typically, liquids and gases are used as coolants. For a coolant to be efficient, it must have a high specific heat.

Ans B)

Answer 2

1. A - dissolving ammonium nitrate in water to cool the water
2. A-  dissolving ammonium nitrate in water to cool the water
3. B-  a liquid with a high specific heat