Question

Combustion of glucose takes place according to the equation.
${C_6}{H_{12}}{O_6} + 6{O_2} \to 6C{O_2} + 6{H_2}O$
$\Delta H = 0 = - 72Kcal$
The energy required for the combustion of 1.6 g of glucose is:
A.$0.064kcal$
B.$0.64kcal$
C.$6.4kcal$
D.$64kcal$

Answer 1

Hint: The enthalpy of the reaction is defined as the energy released during the reaction in the form of heat when one mole of any compound burns completely in presence of oxygen. The enthalpy is denoted by $\Delta H$.

Complete step by step answer:
A combustion reaction is a type of reaction in which a given compound reacts with the oxygen gas and
As a result energy is released in the form of light.
Example of combustion reaction:
Hydrogen gas reacts with oxygen to give water vapors.
The reaction for the combustion of hydrogen gas is shown below.
$2{H_2}(g) + {O_2}(g) \to 2{H_2}O(g)$
According to the question, the formation of glucose can be shown as given below.
$6C{O_2} + 6{H_2}O + 72Cal \to {C_6}{H_{12}}{O_6} + 6{O_2}$
The molecular mass of glucose is 180 g/mol.
For the generation of 180 gm of glucose $ - 72kcal$ is required.
Given, the mass of glucose is 1.6 g.
To calculate the moles of glucose divide given mass of glucose with the molecular mass.
The formula to calculate moles is shown below.
$n = \dfrac{m}{M}$
Where,
n is the moles of glucose.
m is the given mass of the glucose.
M is the molar mass of glucose.
To calculate the moles of glucose, substitute the given values in the above expression as shown below.
$n = \dfrac{{1.6}}{{180}}$
$\Rightarrow n = 0.008$
The calculation for the energy needed for the production of 1.6 gm of glucose is shown below.
$E = \dfrac{{ - 72}}{{180}} \times 1.6$
$\Rightarrow E = - 0.64kcal$
The minus sign shows that the energy is released.
Thus, the energy required for the production of 1.6 g of glucose is 0.64 k cal.
Therefore, the correct option is B.

Note:
Combustion reaction is an exothermic process. The process where energy is released in the form
of heat is termed an exothermic process. In this process the change in enthalpy is always negative.