Final answer:
To calculate the standard free energy of formation for phosphoric acid, we apply Hess's Law using the given standard free energies for phosphorus, phosphorus pentoxide, water, and oxygen to find the resulting ΔG° for phosphoric acid.
Step-by-step explanation:
The student is asking for the calculation of the standard free energy of formation, ΔG°, for phosphoric acid (H3PO4). To find this, we will use the given standard free energies of formation for other substances and apply Hess's Law to deduce the ΔG° for phosphoric acid.
In the reaction provided, phosphorus (P4) reacts with oxygen to form phosphoric acid (H3PO4), we can use the following equation derived from Hess's Law:
ΔG° (H3PO4) = ΔG° (formation of P4O10) + 6 ΔG° (formation of H2O) - ΔG° (formation of P4) - ΔG° (formation of O2)
By combining the given values, we can calculate:
ΔG° (H3PO4) = (-428.66 kJ/mol) + 6(-457.18 kJ/mol) - (-2697.0 kJ/mol)
Substituting all the values in and solving the equation will give the ΔG° for phosphoric acid.