Question

Use the standard enthalpy of formation values to calculate the enthalpy of reaction (∆rH°) for the balanced reaction of ethane (C2H6) with oxygen gas to form carbon dioxide gas and water vapor (in kJ). Do not include units in your answer. Hint: When you write the balanced chemical reaction, be sure to use the lowest whole number and not fractions. Note: We find a way to estimate this value using bond strengths in an upcoming whole class meeting.

Answer 1

The enthalpy of reaction for the combustion of ethane with oxygen to form carbon dioxide and water vapor is -2850.4 kJ/mol.

Step-by-step explanation:

To calculate the enthalpy of reaction (∆rH°) using standard enthalpy of formation values for the combustion of ethane (C2H6) with oxygen gas (O2), we first need to write a balanced chemical equation:

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

Now we can use the standard enthalpy of formation values:

• ∆fH° for C2H6(g) = -84.7 kJ/mol
• ∆fH° for CO2(g) = -393.5 kJ/mol
• ∆fH° for H2O(g) = -241.8 kJ/mol

Enthalpy of reaction calculation:

∆rH° = [Σ(∆fH° products) - Σ(∆fH° reactants)] = [4(-393.5) + 6(-241.8)] - [2(-84.7)]

∆rH° = [-1574 + -1450.8] - [-169.4]

∆rH° = -2850.4 kJ/mol

Answer 2

To calculate the enthalpy of reaction for the combustion of ethane, one must use the standard enthalpy of formation values for each reactant and product, considering their coefficients in the balanced reaction equation. The sum of the enthalpies of the products minus the sum of the enthalpies of the reactants gives the enthalpy of reaction.

Step-by-step explanation:

Enthalpy of Combustion for Ethane

The student is asked to calculate the enthalpy of reaction (ΔrH°) for the combustion of ethane (C2H6) with oxygen to form carbon dioxide and water vapor.

This calculation uses the standard enthalpy of formation values. The balanced equation for the combustion of ethane is C2H6(g) + 7/2 O2(g) → 2 CO2(g) + 3 H2O(g).

To solve this, remember that the enthalpy of reaction can be found using the sum of the enthalpy of formation of the products minus the sum of the enthalpy of formation of the reactants.

However, we need to multiply the enthalpies of formation by the stoichiometric coefficients from the balanced equation.

Calculation Steps

Write the balanced equation for the reaction.

Find the standard enthalpy of formation for each reactant and product.

Multiply the enthalpy of formation by the coefficient in the balanced equation.

Sum the total enthalpy of formation for the products, and do the same for the reactants.

Subtract the sum for the reactants from the sum for the products to give the enthalpy of the reaction.

To calculate the heat of combustion for one mole of ethanol, we look at the balanced equation: C2H5OH(l) + 3 O2(g) → 2 CO2(g) + 3 H2O(l).

Using the enthalpies of formation provided: for ethanol -278 kJ/mol, water -286 kJ/mol (each), and carbon dioxide -394 kJ/mol (each), we can perform similar steps to find the enthalpy of reaction for this combustion process.