Bond Energy Chem Worksheet 16 2 Answers Pdf
Bond Energy Chem Worksheet 16 2 Answers Pdf
Bond energy is the amount of energy required to break a bond between two atoms. It is also the amount of energy released when a bond is formed. Bond energy can be used to calculate the enthalpy change of a chemical reaction by comparing the energy of the bonds in the reactants and the products. This article will explain how to use bond energy data to solve some chemistry problems, and provide some examples of bond energy worksheets with answers.
How to use bond energy data
To calculate the enthalpy change of a reaction using bond energy data, we need to follow these steps:
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Draw the Lewis structures of the reactants and the products, and identify the bonds that are broken and formed.
Find the bond energy values for each bond from a table or a database. The bond energy values are usually given in kilojoules per mole (kJ/mol).
Multiply the bond energy values by the number of bonds that are broken and formed, and add them up to get the total energy of breaking and forming bonds.
Subtract the total energy of forming bonds from the total energy of breaking bonds. This gives the enthalpy change of the reaction.
If the enthalpy change is negative, it means that the reaction is exothermic (releases heat). If the enthalpy change is positive, it means that the reaction is endothermic (absorbs heat).
The general formula for calculating the enthalpy change using bond energy data is:
$$\Delta H_rxn = \sum E_bonds \; broken - \sum E_bonds \; formed$$
Examples of bond energy worksheets with answers
Here are some examples of bond energy worksheets with answers, based on some web search results . You can use these worksheets to practice your skills in using bond energy data.
Example 1
Calculate the enthalpy change for the following reaction using bond energy data:
$$H_2(g) + F_2(g) \rightarrow 2HF(g)$$
Bonds broken
Bonds formed
1 H-H (436 kJ/mol)
2 H-F (565 kJ/mol)
1 F-F (155 kJ/mol)
Total = 591 kJ/mol
Total = 1130 kJ/mol
The enthalpy change is:
$$\Delta H_rxn = \sum E_bonds \; broken - \sum E_bonds \; formed$$ $$\Delta H_rxn = 591 - 1130$$ $$\Delta H_rxn = -539 \; kJ/mol$$ The reaction is exothermic, as it releases more energy than it absorbs.
Example 2
Calculate the enthalpy change for the following reaction using bond energy data:
$$CH_4(g) + Cl_2(g) \rightarrow CH_3Cl(g) + HCl(g)$$
Bonds broken
Bonds formed
4 C-H (413 kJ/mol)
3 C-H (413 kJ/mol)
1 Cl-Cl (242 kJ/mol)
1 C-Cl (339 kJ/mol)
1 H-Cl (431 kJ/mol)
Total = 1894 kJ/mol
Total = 1936 kJ/mol
The enthalpy change is:
$$\Delta H_rxn = \sum E_bonds \; broken - \sum E_bonds \; formed$$ $$\Delta H_rxn = 1894 - 1936$$ $$\Delta H_rxn = -42 \; kJ/mol$$ The reaction is slightly exothermic, as it releases a small amount of energy.
Example 3
Calculate the enthalpy change for the following reaction using bond energy data:
$$2H_2O(g) \rightarrow 2H_2(g) + O_2(g)$$
Bonds broken
Bonds formed
4 O-H (463 kJ/mol)
2 H-H (436 kJ/mol)
1 O=O (498 kJ/mol)
Total = 1852 kJ/mol
Total = 1370 kJ/mol
The enthalpy change is:
$$\Delta H_rxn = \sum E_bonds \; broken - \sum E_bonds \; formed$$ $$\Delta H_rxn = 1852 - 1370$$ $$\Delta H_rxn = +482 \; kJ/mol$$ The reaction is endothermic, as it absorbs more energy than it releases.
References
: Bond Energy Keys - mrsq.net : Bond Energy Worksheet Answers - Ms McRae's Science : BOND ENERGY CALCULATIONS 1 - scisheets.co.uk