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Multiple Choice
Use the bond energies in Chemistry 2e of your textbook to determine the approximate enthalpy change for the following reaction: H2(g) + 1/2 O2(g) → H2O(g). What is the approximate enthalpy change (ΔH) for this reaction?
A
-242 kJ/mol
B
-198 kJ/mol
C
-285 kJ/mol
D
-184 kJ/mol
Verified step by step guidance
1
Identify the bonds broken and formed in the reaction. In the reaction H2(g) + 1/2 O2(g) → H2O(g), the bonds broken are one H-H bond and half an O=O bond. The bonds formed are two O-H bonds in water.
Use the bond energies from your textbook to find the energy required to break the bonds. Look up the bond energy for the H-H bond and the O=O bond. Calculate the total energy required to break these bonds.
Calculate the energy released when new bonds are formed. Look up the bond energy for the O-H bond and calculate the total energy released when two O-H bonds are formed.
Determine the enthalpy change (ΔH) for the reaction by subtracting the total energy of the bonds formed from the total energy of the bonds broken. This can be expressed as: ΔH = (Energy of bonds broken) - (Energy of bonds formed).
Compare the calculated ΔH with the given options to determine which one is closest to your calculated value. This will help you identify the correct approximate enthalpy change for the reaction.