Question

How do you calculate the energy change of reaction for the following reaction ?

Answer 1

Hint: Enthalpy change of the response is characterized as the distinction of all out enthalpy change of the item and the all out enthalpy change of the reactants. It is spoken to as . It is negative for exothermic responses and positive for endothermic responses .

Complete step by step answer:
The energy change in a response can be determined utilizing bond energies. A bond energy is the measure of energy expected to break one mole of a specific covalent bond.
Various bonds have distinctive bond energies. These are given when they are required for computations.
To figure an energy change for a response:
1.Add together the bond energies for all the bonds in the reactants : this is the energy in
2.Add together the bond energies for all the bonds in the things : this is the energy out
3.Energy change = Energy in - Energy out
Example-
Hydrogen and chlorine respond to frame hydrogen chloride gas:
\[H - H{\text{ }} + {\text{ }}Cl - Cl{\text{ }} \to {\text{ }}2{\text{ }} \times {\text{ }}\left( {H - Cl} \right)\]
Utilize the bond energies in the table to figure the energy change for this response.
 Bond - Bond energy
\[\begin{array}{*{20}{l}}
  {H - H\; - \;\;\;436{\text{ }}kJ{\text{ }}mo{l^{ - 1}}\;} \\
  {Cl - Cl\; - \;243{\text{ }}kJ{\text{ }}mo{l^{ - 1}}\;} \\
  {H - Cl\; - \;\;432{\text{ }}kJ{\text{ }}mo{l^{ - 1}}\;}
\end{array}\]
Energy in = \[436{\text{ }} + {\text{ }}243{\text{ }} = {\text{ }}679{\text{ }}kJ{\text{ }}mo{l^{ - 1}}\]
Energy out = \[\left( {2{\text{ }} \times {\text{ }}432} \right){\text{ }} = {\text{ }}864{\text{ }}kJ{\text{ }}mo{l^{ - 1}}\]
Energy change = In - Out
\[ = {\text{ }}679{\text{ }} - {\text{ }}864{\text{ }} = {\text{ }} - {\text{ }}185{\text{ }}kJ{\text{ }}mo{l^{ - 1}}\]
The energy change is negative. This shows that the response is exothermic.
Example -
Hydrogen bromide decays to frame hydrogen and bromine:
\[2{\text{ }} \times {\text{ }}\left( {H - Br} \right){\text{ }} \to {\text{ }}H - H{\text{ }} + {\text{ }}Br - Br\]
Utilize the bond energies in the table to figure the energy change for this response.
Bond - Bond energy
\[\begin{array}{*{20}{l}}
  {H - H\; - \;\;\;436{\text{ }}kJ{\text{ }}mo{l^{ - 1}}\;} \\
  {Cl - Cl\; - \;243{\text{ }}kJ{\text{ }}mo{l^{ - 1}}\;} \\
  {H - Cl\; - \;\;432{\text{ }}kJ{\text{ }}mo{l^{ - 1}}\;}
\end{array}\]
Energy in = \[2{\text{ }} \times {\text{ }}366{\text{ }} = {\text{ }}732{\text{ }}kJ{\text{ }}mo{l^{ - 1}}\;\]
Energy out = 4\[436{\text{ }} + {\text{ }}193{\text{ }} = {\text{ }}629{\text{ }}kJ{\text{ }}mo{l^{ - 1}}\;\]
Energy change = In - Out
\[ = {\text{ }}732{\text{ }} - {\text{ }}629{\text{ }} = {\text{ }} + 103{\text{ }}kJ{\text{ }}mo{l^{ - 1}}\]
The energy change is positive. This shows that the response is endothermic.

Note:
We need to figure out what bonds are broken and what bonds are shaped. Bond breaking is endothermic-we need to place energy into breaking the bond so the incentive for ΔH will be positive. Bond making is exothermic, which means energy will be delivered to the environmental factors and ΔH will be negative.