2C6H6(l) + 15O2 (g) ---> 12CO2 (g) + 6H2 (l)
Calculate the deltaHrxn using standard heats of formations from Appendix C, paying close attention to the physical states of substances.
Thanks!
dHrxn = (n*dHf products) - (n*dHf reactants)
To calculate the deltaHrxn using standard heats of formations, we need to use the standard heat of formation values for each component involved in the reaction. The standard heat of formation, denoted as ΔH°f, represents the enthalpy change when one mole of a compound is formed from its elements in their standard states.
From Appendix C, we can find the standard heats of formation for the compounds involved in the reaction:
ΔH°f of CO2(g) = -393.5 kJ/mol
ΔH°f of H2(l) = 0 kJ/mol
ΔH°f of C6H6(l) = 49.0 kJ/mol
ΔH°f of O2(g) = 0 kJ/mol
Now, let's calculate the deltaHrxn using these standard heats of formation values for the reaction:
ΔH°rxn = Σ(nΔH°f(products)) - Σ(nΔH°f(reactants))
First, we need to determine the stoichiometric coefficients (n) for each compound involved in the reaction:
2C6H6(l) + 15O2(g) ---> 12CO2(g) + 6H2(l)
n(C6H6) = 2
n(O2) = 15
n(CO2) = 12
n(H2) = 6
ΔH°rxn = (12mol x ΔH°f(CO2)) + (6mol x ΔH°f(H2)) - (2mol x ΔH°f(C6H6)) - (15mol x ΔH°f(O2))
Substituting the values:
ΔH°rxn = (12mol x -393.5 kJ/mol) + (6mol x 0 kJ/mol) - (2mol x 49.0 kJ/mol) - (15mol x 0 kJ/mol)
Calculating:
ΔH°rxn = -4722.0 kJ
Therefore, the deltaHrxn for the given reaction is -4722.0 kJ.
To calculate the deltaHrxn using standard heats of formations, you need to follow these steps:
1. Write down the balanced chemical equation for the reaction, taking into account the physical states of the substances. In this case, the given chemical equation is:
2C6H6(l) + 15O2(g) ---> 12CO2(g) + 6H2(l)
2. Look up the standard heats of formation (ΔH°f) for each of the substances involved in the reaction. The standard heat of formation is the enthalpy change when one mole of a compound is formed from its elements in their standard states. You can find these values in Appendix C of your chemistry textbook or online resources.
For this reaction, you need the standard heats of formation for the following compounds:
- ΔH°f(C6H6(l)) : Standard heat of formation for liquid benzene
- ΔH°f(O2(g)): Standard heat of formation for gaseous oxygen
- ΔH°f(CO2(g)) : Standard heat of formation for gaseous carbon dioxide
- ΔH°f(H2(l)) : Standard heat of formation for liquid hydrogen gas
3. Multiply the stoichiometric coefficients of each substance by its corresponding standard heat of formation.
In this case, the equation is already balanced, so you can directly multiply the coefficients:
ΔHrxn = (2 × ΔH°f(C6H6(l))) + (15 × ΔH°f(O2(g))) - (12 × ΔH°f(CO2(g))) - (6 × ΔH°f(H2(l)))
4. Calculate the value of ΔHrxn using the obtained values from step 3.
Make sure to use the appropriate unit for the standard heats of formation and perform the calculations accurately to get the final value of ΔHrxn.
Note: If the standard heats of formation are given in units other than kilojoules per mole (kJ/mol), you may need to convert them to the appropriate unit before performing the calculation.
I hope this explanation helps you to calculate the deltaHrxn! Let me know if you have any further questions.