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Why do polystyrene coffee cup calorimeters give less accurate results than research calorimeters?
AThey cannot hold enough of the reacting solution
BThey react chemically with most acids and bases
CThey allow more heat exchange with the outside
DThey cannot be fitted with a stirrer or a cover
Answer & Solution
Correct answer: C. They allow more heat exchange with the outside
1. Accurate work needs a calorimeter that all but prevents heat exchange with its environment.
2. Research calorimeters use a well insulated, fully enclosed vessel to achieve that.
3. Simple polystyrene cups insulate less well, so heat leaks in or out.
4. That leakage makes the measured temperature change wrong, giving less accurate energy values.
5. A thermometer and stirrer can be fitted through the cover, so that is not the limitation.
_Source: OpenStax Chemistry (CC BY 4.0), Ch 5 "Thermochemistry", section 5.2 Calorimetry_
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