A specialty chemical facility synthesizes pure solid benzoic acid (C₆H₅CO₂H) by oxidizing liquid toluene (C₆H₅CH₃) in two discrete reactors and then crystallizing the product. The following data apply at 298 K and 1 bar.
Step
Chemical transformation
ΔH (kJ mol⁻¹)
1
C₆H₅CH₃(l) + O₂(g) → C₆H₅CH₂OH(l)
–247.9
2
C₆H₅CH₂OH(l) + O₂(g) → C₆H₅CO₂H(l) + H₂O(l)
–371.4
3
C₆H₅CO₂H(l) → C₆H₅CO₂H(s)
–10.6
Molar mass of benzoic acid = 122.12 g mol⁻¹.
(a) Combine the three steps into one overall balanced chemical equation for producing solid benzoic acid from liquid toluene and gaseous oxygen.
(b) Determine the overall enthalpy change per mole of benzoic acid formed.
(c) Calculate the enthalpy change per kilogram of solid benzoic acid produced, reporting the result to three significant figures.
(d) If the plant produces 2.00 × 10³ kg of benzoic acid per day, estimate the daily heat that must be removed (or supplied) solely because of the chemistry and crystallization. State whether heat removal or heat input is required and justify your answer based on the sign of the enthalpy change.