Question

The unit of calorific value is:
A. kJ/kg
B. kg/kJ
C. kB/kJ
D. g/kJ

Answer 1

Hint: From the calorific word we can take the hint that it is something that is related to the energy term. We can find units from balancing units of any equation or formula or any given definition.

Complete step by step answer:
Here we know that it is the amount of energy produced by the complete combustion of a material or fuel at constant pressure and under normal (standard) conditions. And it is measured in units of energy per amount of material. And calorific value can be determined using heat balance. Heat given by the fuel is equal to the heat gained by the water. So,
Mass of fuel x calorific value =mass of water x specific heat x change in temperature, and here
Unit of mass of fuel = kg,
Unit of calorific value = ?,
Unit of mass of water = kg,
Unit of specific heat = J/kg K,
Unit of temperature = K.
By applying unit balance in heat balance equation and putting above units in the formula:
(kg) x (Unit of calorific value) = (kg) x (J/kg K) x (K)
So, the unit of calorific value = J/kg
We can also take kilo J.
Also, from the definition of calorific value we can find the unit of calorific value
= amount of energy produced by combustion of material = (joule/ kg) or (kilo joule/ kg)
So, the answer is “A”.

Note: This unit of calorific value should satisfy the energy balance equation. And here, we have to be careful while taking units of energy, mass and specific heat, etc.