Question

Combustion of glucose takes place according to the equation:
${{\text{C}}_{\text{6}}}{{\text{H}}_{\text{12}}}{{\text{O}}_{\text{6}}}\text{+6}{{\text{O}}_{\text{2}}}\to \text{6C}{{\text{O}}_{\text{2}}}\text{+6}{{\text{H}}_{\text{2}}}\text{O, }\Delta \text{H = -72kcal}$
The energy required for the production of 1.6 g of glucose is [molecular mass of glucose is 180 g).
(A) 0.064 kcal
(B) 0.64 kcal
(C) 6.4 kcal
(D) 64 kcal

Answer 1

Hint: Use the value of molecular mass of glucose and relate it to value of heat of combustion provided in the question. As per the question, combustion of 180 g of glucose utilizes 72 kcal energy.

Complete step by step answer:
According to the question, complete combustion of energy has a latent heat equal to 72 kcal.
Since, Molar mass of glucose = 180 g/mol
Therefore, Energy required by 180 g glucose = 72 kcal
Energy required by 1 g glucose = $\dfrac{72}{180}$ kcal
Energy required by 1.6 g glucose = $\dfrac{72}{180}\text{ x 1}\text{.6 kcal }$= 0.64 kcal
Therefore, the answer is – option (b) – The energy required for the production of 1.6 g of glucose is 0.64 kcal.

Additional Information: “Combustion, or burning, is a high-temperature exothermic redox chemical reaction between a fuel and an oxidant, usually atmospheric oxygen, that produces oxidized, often gaseous products, in a mixture termed as smoke”.

Note: $\Delta \text{H}$ given in the question refers to latent heat.
“Latent heat is a thermodynamic quantity equivalent to the total heat content of a system. It is equal to the internal energy of the system plus the product of pressure and volume”. A negative heat of enthalpy means that the reaction is exothermic and is very feasible.