How to calculate bond energy for a reaction?
Answers
Answered by
0
How to Calculate Bond Energy
Bond energy is an important concept in chemistry that defines the amount of energy needed to break a bond between a covalently bound gas.[1] This type of bond energy does not apply to ionic bonds.[2] When two atoms bind together to form a new molecule, it is possible to determine how strong the bond between atoms is by measuring the amount of energy needed to break that bond. Remember, a single atom does not have a bond energy; it is the bond between two atoms that has energy. To calculate the bond energy of a reaction, simply determine the total number of bonds broken and then subtract the total number of bonds formed.
Part One of Two:
Determining the Broken and Formed Bonds

1
Define the equation for calculating bond energy. Bond energy is defined by the sum of all of the bonds broken minus the sum of all of the bonds formed: ΔH = ∑H(bonds broken) - ∑H(bonds formed). ΔH is the change in bond energy, also referred to as the bond enthalpy and ∑H is the sum of the bond energies for each side of the equation.[3]This equation is a form of Hess’s Law.The unit for bond energy is kilojoules per mol or kJ/mol.[4]

2
Draw the chemical equation showing all of the bonds between molecules.When given an equation simply written with chemical symbols and numbers, it is helpful to draw this equation out, illustrating all of the bonds formed between the various elements and molecules. This visual representation will allow you to easily count all of the bonds that break and form on the reactant and product sides of the equation.Remember, the left side of the equation is all of the reactants and the right side is all of the products.Single, double, and triple bonds have different bond energies, so be sure to draw your diagram with the correct bonds between elements.[5]For example, draw out the following equation: H2(g) + Br2(g) ---> 2 HBr(g)H-H + Br-Br ---> 2 H-Br

3
Know the rules for counting broken and formed bonds. In most cases, the bond energies you will be using for these calculations will be averages.[6] The same bond can have a slightly different bond energy based on the molecule it is formed in; therefore, average bond energies are generally used.[7].A single, double, and triple bond are all treated as one break. They all have different bond energies, but count as only a single break.The same is true for the formation of a single, double, or triple bond. It will be counted as single formation.For our example, all of the bonds are single bonds.

4
Identify the bonds broken on the left side of the equation. The left side contains the reactants. These will represent all of the broken bonds in the equation. This is an endothermic process that requires the absorption of energy to break the bonds.[8]For our example, the left side has 1 H-H bond and 1 Br-Br bond.

5
Count the bonds formed on the right side of the equation. The right side contains all of the products. These are all of the bonds that will be formed. This is an exothermic process that releases energy, usually in the form of heat.[9]For our example, the right side has 2 H-Br bonds.
Bond energy is an important concept in chemistry that defines the amount of energy needed to break a bond between a covalently bound gas.[1] This type of bond energy does not apply to ionic bonds.[2] When two atoms bind together to form a new molecule, it is possible to determine how strong the bond between atoms is by measuring the amount of energy needed to break that bond. Remember, a single atom does not have a bond energy; it is the bond between two atoms that has energy. To calculate the bond energy of a reaction, simply determine the total number of bonds broken and then subtract the total number of bonds formed.
Part One of Two:
Determining the Broken and Formed Bonds

1
Define the equation for calculating bond energy. Bond energy is defined by the sum of all of the bonds broken minus the sum of all of the bonds formed: ΔH = ∑H(bonds broken) - ∑H(bonds formed). ΔH is the change in bond energy, also referred to as the bond enthalpy and ∑H is the sum of the bond energies for each side of the equation.[3]This equation is a form of Hess’s Law.The unit for bond energy is kilojoules per mol or kJ/mol.[4]

2
Draw the chemical equation showing all of the bonds between molecules.When given an equation simply written with chemical symbols and numbers, it is helpful to draw this equation out, illustrating all of the bonds formed between the various elements and molecules. This visual representation will allow you to easily count all of the bonds that break and form on the reactant and product sides of the equation.Remember, the left side of the equation is all of the reactants and the right side is all of the products.Single, double, and triple bonds have different bond energies, so be sure to draw your diagram with the correct bonds between elements.[5]For example, draw out the following equation: H2(g) + Br2(g) ---> 2 HBr(g)H-H + Br-Br ---> 2 H-Br

3
Know the rules for counting broken and formed bonds. In most cases, the bond energies you will be using for these calculations will be averages.[6] The same bond can have a slightly different bond energy based on the molecule it is formed in; therefore, average bond energies are generally used.[7].A single, double, and triple bond are all treated as one break. They all have different bond energies, but count as only a single break.The same is true for the formation of a single, double, or triple bond. It will be counted as single formation.For our example, all of the bonds are single bonds.

4
Identify the bonds broken on the left side of the equation. The left side contains the reactants. These will represent all of the broken bonds in the equation. This is an endothermic process that requires the absorption of energy to break the bonds.[8]For our example, the left side has 1 H-H bond and 1 Br-Br bond.

5
Count the bonds formed on the right side of the equation. The right side contains all of the products. These are all of the bonds that will be formed. This is an exothermic process that releases energy, usually in the form of heat.[9]For our example, the right side has 2 H-Br bonds.
Similar questions