Question

The heat produced by burning $1$ g of fuel completely is known as
A. Heat capacity
B. Calorific value
C. Vapour density
D. Boiling point

Answer 1

When $1$ g of fuel burns completely it produces energy in form of heat. The heat is measured in terms of energy released. The unit of energy is joule, kilojoule, calorie or kilocalorie.

Complete answer:
Heat capacity is the heat required to increase the temperature of a substance ${\text{1}}{\,^{\text{o}}}{\text{C}}$.

The heat released during the complete combustion of the fuel is defined in joule per kilogram. Joule is the unit of energy. So, the heat released during the complete combustion of the fuel is the energy produced in joule by burning one kilogram of fuel. A calorie is also the unit of energy. So, the heat released during the complete combustion of the fuel is known as calorific value.

The density of a gas or vapour with respect to the hydrogen at a particular temperature and pressure is known as vapour density.

The temperature at which the vapour pressure of a liquid becomes equal to the atmospheric vapour pressure and the complete liquid converts into gas is known as boiling point.

So, the heat produced by burning $1$ g of fuel completely is known as calorific value.

Therefore, the correct answer is option (B) ‘Calorific value’.

Note: The burning of saturated or unsaturated hydrocarbons in presence of oxygen is known as combustion. The combustion of a hydrocarbon produces carbon dioxide, water, heat, and light. Heat capacity is the heat required to increase the temperature whereas the calorific value is the heat released. Calorific value is determined for complete combustion. The saturated hydrocarbon burns completely. The unsaturated hydrocarbon burns incompletely.