Question

The calorific values of lipids and carbohydrates respectively, are:
(A) $\dfrac{{15.3\dfrac{{Kcals}}{g}}}{{9.3\dfrac{{Kcals}}{g}}}$
(B) $\dfrac{{4.5\dfrac{{Kcals}}{g}}}{{9.3\dfrac{{Kcals}}{g}}}$
(C) $\dfrac{{3.9\dfrac{{Kcals}}{g}}}{{9.3\dfrac{{Kcals}}{g}}}$
(D) $\dfrac{{9.3\dfrac{{Kcals}}{g}}}{{4.5\dfrac{{Kcals}}{g}}}$

Answer 1

Let’s first see what calorific value is. So, the Calorific value is nothing but the energy contained in a fuel or food, determined by measuring the heat produced by the complete combustion of a specified quantity of it. This is now usually expressed in joules per kilogram.

Complete answer:
Calorific value is the amount of energy released or produced when one kg of fuel burns or any other substance is burnt in the presence of oxygen and the products of combustion are cooled to $STP$ . Its $SI$ unit is $\dfrac{{KJ}}{{Kg}}$ .
There are two kinds of enthalpy of combustion, called higher and lower heating value, depending on how much the products are allowed to cool and whether compounds like ${H_2}O$ are allowed to condense. The high heat values are conventionally measured with a bomb calorimeter.
The calorific value of lipid and carbohydrates are $\dfrac{{9.3\dfrac{{Kcals}}{g}}}{{4.5\dfrac{{Kcals}}{g}}}$
So, the correct answer is (D) $\dfrac{{9.3\dfrac{{Kcals}}{g}}}{{4.5\dfrac{{Kcals}}{g}}}$ .

Additional Information:
There are two kinds of enthalpy of combustion, called higher and lower heating value, depending on how much the products are allowed to cool and whether compounds like ${H_2}O$ are allowed to condense. The high heat values are conventionally measured with a bomb calorimeter. Low heat values are calculated from high heat value test data. They may also be calculated as the difference between the heat of formation $\Delta {H^\theta }$ f of the products and reactants.

Note:
Calorific value, measured in British thermal units or megajoules per kilogram, is the amount of chemical energy stored in a coal that is released as thermal energy upon combustion. It is directly related to rank; in fact, the $ASTM$ method uses calorific value.