What is the heat of combustion of ethane, c2h6, in kilojoules per mole of ethane? Enthalpy of formation values can be found in t

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oksian1 [2.3K]

2 years ago

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What is the heat of combustion of ethane, c2h6, in kilojoules per mole of ethane? Enthalpy of formation values can be found in t

his list of thermodynamic properties?

Chemistry

2 answers:

Andre45 [30] · Answer 1 · 2022-02-20T18:23:15+03:00

The balanced combustion reaction for one mole of ethane will be

C2H6 + 3.5 O2 ---> 2CO2(g) + 3H2O (l)

Enthalpy of reaction of combustion = ∑ΔHf (products)- ∑ΔHf (reactant)

ΔHf = enthalpy of formation

The enthalpy of formation of oxygen = 0 as it is an element in its native state

ΔHf C2H6 = -83.820 kJ / mole

ΔHf H2O = -285.830 kJ / mole

ΔHf CO2 = -393.509 kJ / mole

ΔHrxn = [2 X ΔHf CO2 + 3 X ΔHf H2O] - [ΔHf C2H6]

ΔHrxn = [2 X (-393.509) + 3 (-285.830)] - [-83.820]

ΔHrxn = -1560.688 kJ / mole

ludmilkaskok [199] · Answer 2 · 2022-02-20T19:31:19+03:00

The heat of combustion of ethane C₂H₆: <u>-1559.9 kJ / mol </u>

<h3>Further explanation </h3>

The change in enthalpy in the formation of 1 mole of the elements is called enthalpy of formation

The enthalpy of formation measured in standard conditions (25 ° C, 1 atm) is called the standard enthalpy of formation (ΔHf °)

Determination of the enthalpy of formation of a reaction can be through a calorimetric experiment, based on the principle of Hess's Law, enthalpy of formation table, or from bond energy data

Delta H reaction (ΔH) is the amount of heat / heat change between the system and its environment

(ΔH) can be positive (endothermic = requires heat) or negative (exothermic = releasing heat)

The value of ° H ° can be calculated from the change in enthalpy of standard formation:

<h3>∆H ° rxn = ∑n ∆Hf ° (product) - ∑n ∆Hf ° (reactants) </h3>

ΔH∘rxn = ΔH∘f of the product (s) if ∆Hf ° (reactants) = 0

<em>The elements in standard conditions are not included in the enthalpy calculations because the enthalpy of those elements under the standard conditions is </em><u><em>zero. </em></u>

The reaction of the combustion of hydrocarbons with oxygen produces CO₂ and H₂O (water vapor )

Hydrocarbon combustion reactions (specifically alkanes)

[tex] \large {\box {\bold {C_nH _ (_2_n _ + _ 2_) + \frac {3n + 1} {2} O_2 ----> nCO_2 + (n + 1) H_2O}}} [ /tex]

From data on the internet:

∆H ° f H₂O: -285.8 kJ

°H ° f CO₂: -393.5 kJ

°H ° f C₂H₆: -84.7 kJ

Combustion of ethane, C₂H₆

2C₂H₆ (g) + 7O₂ (g) ⟶ 4CO₂ (g) + 6H₂O (l)

= {[4 (∆H ° f CO₂ (g))] + [6 (∆H ° f H₂O (l))]} - {2 [∆H ° f C₂H₆ (g)] + [(7) (∆ H ° f O₂ (g))]}

= {[4 (-393.5 kJ)] + [6 (-285.8 kJ]} - {2 [-84.7 kJ] + [(0 kJ)]}

= -1574 kJ -1714.8 kJ +169.4 kJ