Question

A person requires $2870kcal$ of energy to lead a normal daily life. If heat of combustion of cane sugar is $ - 1349kcal$ , then his daily consumption of sugar is:
A.$728g$
B.$0.728g$
C.$342g$
D.$0.342g$

Answer 1

Hint: We have been given a daily requirement of energy intake and the heat of combustion of that energy. So first we will try to find the heat of combustion for one mole and then for the daily consumption.

Complete step by step answer:
Molar mass of cane sugar $({C_{12}}{H_{22}}{O_{11}})$ is $342.2965g/mol$ .
${\text{number of moles = }}\dfrac{{mass}}{{{\text{molar mass}}}}$
As the energy required for combustion of one mole it is $ - 1349kcal$ .
So now the number of moles required for consumption of $2870kcal$ energy will be
$ \Rightarrow \dfrac{{2870}}{{1349}}$
$ \Rightarrow 2.127moles$
Then his daily consumption will be $2.127 \times 342$
$ \Rightarrow 728g$
As we have been given that a person needs around $2870kcal$ and the heat of combustion is $1349kcal$ , now we have to determine his daily consumption. So he needs $728g$ cane sugar for his daily consumption.
So, option A is correct.

Additional Information:
Combustion reaction involves the reaction of carbon and oxygen containing material together to form carbon dioxide and water as its products.Combustion takes place at high temperature and considered as a high temperature redox reaction. Generally, in the process of combustion, redox reaction takes place between a fuel that is a reductant and oxygen ( usually the oxygen present in the atmosphere) that is an oxidant. Combustion produces oxidized gas mixtures which termed as smoke. If the combustion of an organic compound takes place in the presence of oxygen then that would be the exothermic reaction because the products formed are carbon dioxide and water molecules resulting in the release of energy.

Note:
The heat of combustion is the value of heat released during the burning or breaking down of a substance (food, fuel). Heat of combustion is used in the efforts to reduce the gas consumption from the oil.