Join thousands of students who trust us to help them ace their exams!Watch the first video
Multiple Choice
Use standard enthalpies of formation to calculate ΔH°rxn for the following reaction: CH4(g) + 2O2(g) → CO2(g) + 2H2O(g). Given the following standard enthalpies of formation: CH4(g) = -74.8 kJ/mol, CO2(g) = -393.5 kJ/mol, H2O(g) = -241.8 kJ/mol, O2(g) = 0 kJ/mol.
A
-74.8 kJ/mol
B
-890.3 kJ/mol
C
-802.3 kJ/mol
D
-210.3 kJ/mol
Verified step by step guidance
1
Identify the standard enthalpies of formation for each compound involved in the reaction: CH4(g) = -74.8 kJ/mol, CO2(g) = -393.5 kJ/mol, H2O(g) = -241.8 kJ/mol, and O2(g) = 0 kJ/mol.
Write the balanced chemical equation for the reaction: CH4(g) + 2O2(g) → CO2(g) + 2H2O(g).
Apply the formula for the standard enthalpy change of the reaction (ΔH°rxn): ΔH°rxn = Σ(ΔH°f products) - Σ(ΔH°f reactants).
Calculate the sum of the standard enthalpies of formation for the products: (1 mol CO2 * -393.5 kJ/mol) + (2 mol H2O * -241.8 kJ/mol).
Calculate the sum of the standard enthalpies of formation for the reactants: (1 mol CH4 * -74.8 kJ/mol) + (2 mol O2 * 0 kJ/mol), and then subtract this from the sum of the products to find ΔH°rxn.