Temperature Conversion of a Heat Capacity

Temperature Conversion of a Heat Capacity from CCLI CU-Boulder on Vimeo.

Description: The heat capacity for acetone is converted from SI units to English units, including the necessary temperature conversions.

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Comment by Paul Laibinis on November 18, 2011 at 4:24pm

A nice problem, but the solution does not seem to be correct. Given the conversion of 1 kJ/mole-C = 239 BTU/lbmol-F, the above equations do not yield satisfactory Cps for a common temperature.

For the equations given in the solution:
At 32 F, Cp = 17.1 BTU/lbmol-F. At the same temperature of 0 C, Cp = 0.123 kJ/mol-C. The ratio of these Cps is 139 BTU/lbmol-F per kJ/mol-C, not 239 as it should be.
At 212 F, Cp = 21.6 BTU/lbmol-F. At the same temperature of 100 C, Cp = 0.142 kJ/mol-K. The ratio of these Cps is 152 BTU/lbmol-F per kJ/mol-C, not 239 as it should be. That the conversion factor appears to change in value with temperature suggested that something might be awry.

I think that the answer should instead be 28.6 + 0.025T(deg F). If so, then the ratio between values doesn't change:
At 32 F, Cp = 29.4 BTU/lbmol-F. At the same temperature of 0 C, Cp = 0.123 kJ/mol-C. The ratio of these Cps is 239 BTU/lbmol-F per kJ/mol-C.
At 212 F, Cp = 33.9 BTU/lbmol-F. At the same temperature of 100 C, Cp = 0.142 kJ/mol-K. The ratio of these Cps is 239 BTU/lbmol-F per kJ/mol-C.