Question

2C₄H₁₀ (g) + 13O₂ (g)  →  8CO₂ (g)+ 10H₂O (g)

ΔH_rxn = Σ(bond energy of bonds broken) − Σ(bond energy of bonds formed)Eqn. 1

ΔH_rxn = Σ(ΔH_f, products) − Σ(ΔH_f, reactants)Eqn. 2

Look up all the bond enthalpies for the reactants and products. Calculate the sum of the bond energies (in kJ) in all of the reactants and in all of the products, paying attention to the number of bonds in the molecules and the stoichiometric coefficients for each molecule from the balanced chemical equation. (Enter unrounded values.)

Σ(bond energy of bonds broken)= ----------- kJ

Σ(bond energy of bonds formed)= ----------- kJ

Calculate the enthalpy of combustion, using Eqn. 1. Express the final answer as kJ/mol of butane. Pay attention to the stoichiometric coefficient of the fuel in the balanced chemical equation. (Enter an unrounded value.)

------- kJ/mole of butane

b) Use enthalpies of formation to calculate the enthalpy of combustion for butane with the same balanced reaction written in (a)(i).

(i) Look up all the enthalpies of formation for the reactants and products—make sure you use the value for the correct phase of the species. Calculate the sum of the enthalpies of formation (in kJ) for all of the reactants and all of the products, paying attention to the stoichiometric coefficients for each molecule from the balanced equation. (Enter unrounded values.)

Σ(ΔH_f, reactants)= kJΣ(ΔH_f, products)= ______kJ

(ii) Calculate the enthalpy of combustion, using Eqn. 2. Express the final answer as kJ/mol of butane. Pay attention to the stoichiometric coefficient of the fuel in the balanced chemical equation. (Enter an unrounded value.)

------------ kJ/mol of butane

Part B

The amount of heat that can be obtained from a reaction depends on the amount of reactant used or the amount of product made. The quantity ΔH_rxn in kJ/mol can be used like any other stoichiometric coefficient to relate the amount of heat to the moles of reactant or product used to carry out a reaction. The amount of enthalpy available per kg of fuel is called the energy density of the fuel, and is commonly used to compare the energy content of different sources of energy.

Using your answers from part A (a), answer the following questions.

(a) For butane, C₄H₁₀, calculate the energy released for the combustion of 1 kg of fuel. Express your answer in the units MJ/kg and as the absolute value of the energy. (1 MJ = 1000 kJ.) (Enter an unrounded value.)

--------------- MJ/kg butane

(b) Calculate the kg of carbon dioxide produced per kilogram of fuel for butane. Express your answer as kg CO₂/kg. (Enter an unrounded value.)

--------------- kg CO₂/kg butane

Part C

Diesel is a mixture of hydrocarbons with between 8 and 21 carbon atoms. The average empirical formula for the mixture that is diesel corresponds to C₁₂H₂₃. Biodiesel is a fatty acid ester that can be synthesized from the fatty acids (stearic acid or linoleic acid) in plants or from used cooking oil, such as canola oil or soybean oil. A typical component of biodiesel has the formula C₁₉H₃₆O₂.

(a) Write and balance the combustion reaction for diesel (C₁₂H₂₃) and for biodiesel (C₁₉H₃₆O₂). (Hint: Recall how combustion engines work before answering this question. Include states-of-matter under the given conditions in your answer. Use the lowest possible whole number coefficients.)

Dissel

4C₁₂H₂₃(g) + 71O₂(g) → 48CO₂(g)+46H₂O(g)

Biodiesel

C₁₉H₃₆O₂(g) + 27O₂(g)  → 19CO₂(g)+18H₂O(g)

(b) Calculate the kg of carbon dioxide emitted per kg of diesel and biodiesel. (Enter unrounded values.)

(i) Diesel

________ kg CO₂ / kg diesel

(ii) Biodiesel

________ kg CO₂ / kg biodiesel

Please solve and show work for the questions with the blanks.

Answer 1

2C₄H₁₀ (g) + 13O₂ (g)  →  8CO₂ (g)+ 10H₂O (g)

ΔH_rxn = Σ(bond energy of bonds broken) − Σ(bond energy of bonds formed)Eqn. 1

ΔH_rxn = Σ(ΔH_f, products) − Σ(ΔH_f, reactants)Eqn. 2

Look up all the bond enthalpies for the reactants and products. Calculate the sum of the bond energies (in kJ) in all of the reactants and in all of the products, paying attention to the number of bonds in the molecules and the stoichiometric coefficients for each molecule from the balanced chemical equation. (Enter unrounded values.)

Σ(bond energy of bonds broken)= 16406kJ

Σ(bond energy of bonds formed)= 22160 kJ

Calculate the enthalpy of combustion, using Eqn. 1. Express the final answer as kJ/mol of butane. Pay attention to the stoichiometric coefficient of the fuel in the balanced chemical equation. (Enter an unrounded value.)

-2876.9 kj/mole of butane

b) Use enthalpies of formation to calculate the enthalpy of combustion for butane with the same balanced reaction written in (a)(i).

(i) Look up all the enthalpies of formation for the reactants and products—make sure you use the value for the correct phase of the species. Calculate the sum of the enthalpies of formation (in kJ) for all of the reactants and all of the products, paying attention to the stoichiometric coefficients for each molecule from the balanced equation. (Enter unrounded values.)

Σ(ΔH_f, reactants)= 3131.1kJ    Σ(ΔH_f, products)= 6008kJ

(ii) Calculate the enthalpy of combustion, using Eqn. 2. Express the final answer as kJ/mol of butane. Pay attention to the stoichiometric coefficient of the fuel in the balanced chemical equation. (Enter an unrounded value.)

-2876.9kJ/mol of butane

Part B

The amount of heat that can be obtained from a reaction depends on the amount of reactant used or the amount of product made. The quantity ΔH_rxn in kJ/mol can be used like any other stoichiometric coefficient to relate the amount of heat to the moles of reactant or product used to carry out a reaction. The amount of enthalpy available per kg of fuel is called the energy density of the fuel, and is commonly used to compare the energy content of different sources of energy.

Using your answers from part A (a), answer the following questions.

(a) For butane, C₄H₁₀, calculate the energy released for the combustion of 1 kg of fuel. Express your answer in the units MJ/kg and as the absolute value of the energy. (1 MJ = 1000 kJ.) (Enter an unrounded value.)

2C₄H₁₀ (g) + 13O₂ (g)  →  8CO₂ (g)+ 10H₂O (g)

116g-------------------→2876.9 Kj/mol

1000g-------------------→24800.86kj

24800.86/1000= 24.8 MJ/mole

24.8 MJ/kg butane

(b) Calculate the kg of carbon dioxide produced per kilogram of fuel for butane. Express your answer as kg CO₂/kg. (Enter an unrounded value.)

3.034 kg CO₂/kg butane

Part C

Diesel is a mixture of hydrocarbons with between 8 and 21 carbon atoms. The average empirical formula for the mixture that is diesel corresponds to C₁₂H₂₃. Biodiesel is a fatty acid ester that can be synthesized from the fatty acids (stearic acid or linoleic acid) in plants or from used cooking oil, such as canola oil or soybean oil. A typical component of biodiesel has the formula C₁₉H₃₆O₂.

(a) Write and balance the combustion reaction for diesel (C₁₂H₂₃) and for biodiesel (C₁₉H₃₆O₂). (Hint: Recall how combustion engines work before answering this question. Include states-of-matter under the given conditions in your answer. Use the lowest possible whole number coefficients.)

Dissel

4C₁₂H₂₃(g) + 71O₂(g) → 48CO₂(g)+46H₂O(g)

668g---------→2112g

1000g--------→ 3161g

Biodiesel

C₁₉H₃₆O₂(g) + 27O₂(g)  → 19CO₂(g)+18H₂O(g)

296g-------→836g

1000g-------→2824g