Question

A chemical reaction has a change in enthalpy of 1352 kJ/mol and a total bonding energy of the recants is 1546 kJ/mol. Calculate the total bonding energy of the products and decide whether the reaction is endothermic or exothermic

A)84 kJ/mol, endothermic
B)194 kJ/mol, endothermic
C) 84 kJ/mol, exothermic
D)194 kJ/mol, exothermic

Answer 1

Answer is: D)194 kJ/mol, exothermic
ΔHreaction = ∑(product bond energies) - ∑(reactant bond energies).
∑(product bond energies) = ΔHreaction + ∑(reactant bond energies).
ΔHreaction must be negative (exothermic) if ∑(product bond energies) is positive.
∑(product bond energies) = -1352 kJ/mol + 1546 kJ/mol.
∑(product bond energies) = 194 kJ/mol.
∑ is summation.

Answer 2

Answer: D) 194 kJ/mol, exothermic

Explanation:-

Exothermic reactions are defined as the reactions in which energy of the product is lesser than the energy of the reactants. The total energy is released in the form of heat and $\Delta H$ for the reaction comes out to be negative.

Enthalpy change of the reaction is defined as the difference between the enthalpy change of the products and the enthalpy change of the reactants.

Mathematically,

$\Delta H_{rxn}=H_{products}-H_{reactants}$

For the given reaction:

$\Delta H_{rxn}$= 1352kJ/mol[/tex]

$H_{reactants}=1546kJ/mol$

$-1352kJ/mol=H_{products}-1546kJ/mol$

$H_{products}=194kJ/mol$

The reaction is exothermic as the energy of products is less than the energy of reactants and total bonding energy of the products is 194 kJ.