Chapter 8, Problem 8.85SP

Interpretation Introduction

Interpretation:

Given the formula of a cooking oil, balanced equation for combustion reaction of fat produced from burning of cooking oil has to be written.  The amount of energy released has to be calculated in $kJ/mL$.

Concept Introduction:

Balanced equation

• Every chemical reaction obliges Law for conversion of mass which states the mass of total amount of the product should be equal to the total mass of the reactants.
• The concept of writing a balanced chemical reaction is depends on conversion of reactants into products.
• First write the reaction from the given information.
• Then count the number of atoms of each element in reactants as well as products.
• Finally obtained values could place it as coefficients of reactants as well as products.

Standard heat of formation

Standard heat of formation of a compound is termed as quantity of heat absorbed or evolved at $25°C$ temperature and $1atm$ pressure when one mole of a compound is formed form its constituent elements in pure form under the same reaction conditions at $25°C$ temperature and $1atm$ pressure.

Enthalpy and change in enthalpy

Enthalpy corresponds to heat content of the system and it is represented by ‘H’ and it is the sum of internal energy ‘E’ and product of volume and pressure,

$H=E+PV$

$\Delta H$ refers to change in enthalpy.  Change in enthalpy in a reaction and heat of formation are related by the formula,

$\Delta H_{rxn}^{°}=\Sigma \Delta H_f^{°}(product)-\Sigma \Delta H_f^{°}(reac\tan t)$

Where,

$\begin{array}{l}\Delta H_{rxn}^{°}=\text{ enthalpy change in reaction}\\ \Delta H_f^{°}(product)=\text{ enthalpy or standard heat of formation of product}\\ \Delta H_f^{°}(reac\tan t)=\text{ enthalpy or standard heat of formation of }reac\tan t\end{array}$

$\Delta H$ can also be calculated by,

$\Delta H=\frac{q}{n}$

Where,

$\begin{array}{l}q=heat\text{ absorbed or heat released}\\ \text{n = number of moles}\end{array}$