Answer to Question #149904 in General Chemistry for Nasir Aden

Question

Using the following data,
H2(g) + F2(g) --> 2 HF(g) ΔfH = -537 kJ
C(s) + 2 F2(g) --> CF4(g) ΔfH = -680 kJ
2 C(s) + 2 H2(g) --> C2H4(g) ΔfH = +52.3 kJ

calculates the ΔrH of the reaction of ethylene with fluorine :
C2H4(g) + 6 F2(g) --> 2 CF4(g) + 4 HF(g)

Calculates the standard molar enthalpy of combustion of benzene, C6H6(l). Show all your calculations, including a balanced chemical formula.


Dimethyl ether, C4H10O(l), is a flammable compound that has long been used as a surgical anesthetic. Complete combustion of 1 mole of C4H10O(l) gives ΔcH° = -2723.7 kJ.
Write a balanced equation for the combustion of 1 mole of C4H10O(l).
Calculate the ΔH° of formation of C4H10O(l).
Draw the potential energy diagram of the reaction.

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Answer 1

C₂H₄(g) + 6F₂(g) = 2CF₄(g) + 4HF(g)

ΔH_rxn = ΔH_products - ΔH_reactants = 4 x ΔH(HF) + 2 x ΔH(CF₄) - ΔH(C₂H₄) = 4 x (-537/2) kJ + 2 x (-680) kJ - 52.3 kJ = -338.3 kJ

C₆H₆(l) + 15/2O₂(g) = 6CO₂(g) + 3H₂O(l)

ΔH_rxn = 6 x ΔH(CO₂) + 3 x ΔH(H₂O) - ΔH(C₆H₆)= 6 x (-389.3) + 3 x (-285.8) - 49.0 = -3 242.2 kJ

C₄H₁₀O(l) + 6O₂(g) = 4CO₂(g) + 5H₂O(l)

4C(s) + 5H₂(g) + 1/2O₂(g) = C₄H₁₀O(l), ΔH = -335 kJ/mol