Use standard enthalpies of formation to determine ΔHorxn for:
2C2H2(g) + 5O2(g) → 4CO2(g) + 2H2O(l)
Enter in kJ.
To determine ΔHorxn, we will use the standard enthalpies of formation (∆Hf°) values of the compounds involved in the reaction. The standard enthalpy of formation (∆Hf°) is the enthalpy change when one mole of a compound is formed from its elements in their standard states.
∆Horxn = ∑ (∆Hf° products) - ∑ (∆Hf° reactants)
Let's calculate ∆Horxn step by step:
Reactants:
2C2H2(g) + 5O2(g)
Products:
4CO2(g) + 2H2O(l)
Using the standard enthalpy of formation values:
∆Hf° (C2H2(g)) = 227 kJ/mol
∆Hf° (O2(g)) = 0 kJ/mol
∆Hf° (CO2(g)) = -393.5 kJ/mol
∆Hf° (H2O(l)) = -285.8 kJ/mol
∆Horxn = [4 * ∆Hf° (CO2(g))] + [2 * ∆Hf° (H2O(l))] - [2 * ∆Hf° (C2H2(g))] - [5 * ∆Hf° (O2(g))]
∆Horxn = [4 * (-393.5 kJ/mol)] + [2 * (-285.8 kJ/mol)] - [2 * (227 kJ/mol)] - [5 * (0 kJ/mol)]
Simplifying the equation:
∆Horxn = -1574 kJ/mol + (-571.6 kJ/mol) - 454 kJ/mol
∆Horxn = -1574 kJ/mol - 571.6 kJ/mol - 454 kJ/mol
∆Horxn = -2599.6 kJ/mol
Therefore, the ∆Horxn for the reaction 2C2H2(g) + 5O2(g) → 4CO2(g) + 2H2O(l) is -2599.6 kJ.
To determine ΔHorxn (the standard enthalpy change of a reaction), you need to use the standard enthalpies of formation for each reactant and product. The standard enthalpy of formation (ΔHf°) is the enthalpy change that occurs when one mole of a compound is formed from its elements in their standard states.
First, you need to identify the standard enthalpies of formation for each component of the reaction. Standard enthalpies of formation are typically given in kJ/mol and can be found in reference tables or online databases. For this reaction, you will need the ΔHf° values for C2H2(g), O2(g), CO2(g), and H2O(l).
Next, you can apply the following equation to calculate the ΔHorxn:
ΔHorxn = ∑(νΔHf°products) - ∑(νΔHf°reactants)
Where ν represents the stoichiometric coefficient of each component in the balanced chemical equation.
For the given balanced equation: 2C2H2(g) + 5O2(g) → 4CO2(g) + 2H2O(l)
The stoichiometric coefficients are as follows:
ν(C2H2) = 2
ν(O2) = 5
ν(CO2) = 4
ν(H2O) = 2
Now, you need to look up the standard enthalpy of formation values for each component involved in the reaction. Let's assume the values are as follows:
ΔHf°(C2H2) = 226.73 kJ/mol
ΔHf°(O2) = 0 kJ/mol (since it is an element in its standard state)
ΔHf°(CO2) = -393.51 kJ/mol
ΔHf°(H2O) = -285.83 kJ/mol
Finally, substitute these values into the equation:
ΔHorxn = (2 * ΔHf°(CO2)) + (2 * ΔHf°(H2O)) - (2 * ΔHf°(C2H2)) - (5 * ΔHf°(O2))
ΔHorxn = (2 * (-393.51 kJ/mol)) + (2 * (-285.83 kJ/mol)) - (2 * 226.73 kJ/mol) - (5 * 0 kJ/mol)
Calculate the expression to get the final answer in kJ.