Question

Estimate the mole ratio of O2 to the saple(benzoic acid, sucrose) and compare the estime with stoichiometric ratio for the combustion. The volume of the bomb is 0.3dm^3. Use T=300K and 30atm for the pressure of O2. As a first approximation use the ideal gas law, but more a more refine estimate, use the compressibility factor for O2 at 30atm and 300K as calculated from the Van der Waals equation. Assume ideal behaviour on the part of oxygen

Answer 1

The combustion reaction of benzoic acid is

C6H5COOH + 13/2 O2 ----- > 6CO2 + 3H2O

Hence stoichiometric moles of O2 required for the combustion of benzoic acid = 6.5 mol

The combustion reaction of sucrose is

C12H22O11 + 12 O2 ----- > 12CO2 + 11H2O

Hence stoichiometric moles of O2 required for the combustion of sucrose = 12 mol

Applying ideal gas equation,

moles of O2 inside the bomb calorimeter, n = PV/RT

= (30 atm x 0.3 L) / (0.0821 L.atm.mol-1K-1 x 300K) = 0.36541 mol