Use the bond enthalpy data given to estimate the heat released when 25.0 g of acetylene gas, C₂H₂, burns in excess oxygen to yield carbon dioxide and water vapor at 25^$\circ$C.
BE(C-C) = 347 kJ/mol
BE(C $\equiv$ C) = 812 kJ/mol
BE(C=O in CO₂) = 799 kJ/mol
BE(C-H) = 414 kJ/mol
BE(O-H) = 460 kJ/mol
BE(O=O) = 498.7 kJ/mol

Question

Use the bond enthalpy data given to estimate the heat released when 25.0 g of acetylene gas, C₂H₂, burns in excess oxygen to yield carbon dioxide and water vapor at 25^$\circ$C.
BE(C-C) = 347 kJ/mol
BE(C

\equiv

C) = 812 kJ/mol
BE(C=O in CO₂) = 799 kJ/mol
BE(C-H) = 414 kJ/mol
BE(O-H) = 460 kJ/mol
BE(O=O) = 498.7 kJ/mol

Quizplus · Accepted Answer

The balanced chemical equation for the combustion of acetylene (C2H2) is:$$2C_2H_2(g) + 5O_2(g) \rightarrow 4CO_2(g) + 2H_2O(g)$$To estimate the heat released, we calculate the bond energy for breaking all the bonds in the reactants and forming all the bonds in the products. The difference gives us the heat released.Breaking bonds (requires energy):- 2 C≡C bonds: $2 \times 812 \, \text{kJ/mol}$- 2 C-H bonds: $2 \times 414 \, \text{kJ/mol}$- 5 O=O bonds: $5 \times 498.7 \, \text{kJ/mol}$Forming bonds (releases energy):- 8 C=O bonds: $8 \times 799 \, \text{kJ/mol}$- 4 O-H bonds: $4 \times 460 \, \text{kJ/mol}$Calculate the total energy for breaking and forming bonds:$$ \text{Energy to break bonds} = (2 \times 812) + (2 \times 414) + (5 \times 498.7) $$$$ \text{Energy to form bonds} = (8 \times 799) + (4 \times 460) $$$$ \text{Net energy released} = \text{Energy to form bonds} - \text{Energy to break bonds} $$Given the molar mass of acetylene (C2H2) is approximately 26 g/mol, 25.0 g corresponds to roughly 25.0 / 26 ≈ 0.96 moles. Since the reaction involves 2 moles of C2H2, we adjust the calculated energy for the actual amount of acetylene burned.The calculation will show that the energy released is closest to the value given in option D, 1180 kJ, when considering the stoichiometry and the amount of acetylene burned.

Use the Bond Enthalpy Data Given to Estimate the Heat ∘\circ∘

Use the Bond Enthalpy Data Given to Estimate the Heat $\circ$