Does the oxygen charge affect the calibration of a bomb calorimeter?

Question

Say the bomb vessel is meant to be charged to 30 bar and you charge it to 20 bar with pure oxygen, will this affect the calibration of the bomb vessel? (Will your result still be valid assuming the sample does burn up completely.)

Answer 1

Yes, still valid. The calorimeter measures q, equal to DeltaE because w = 0 (no volume change). This does not depend on P.

There may be a small difference in the calorimeter constant; work it out using the molar specific heat of O2 and PV=nRT for the number of moles missing if you under-pressurise. I'd guess it's negligible.