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Chem 3B Jan 04 question. watch

    • Thread Starter

    The student's evaluation of an experiment is given below.
    " my calculated value of the enthalpy of combustion was numerically much less than the data book value. The reasons for my low value include;
    1) Heat losses to the surrounding air;
    2) when I rechecked the mass of the spirit lamp and ethanol after combustion. I noticed that it had lost mass even when it was not being used;
    3) a black solid which formed on the base of the beaker.

    i) explain why the spirit lamp and ethanol lost mass even when not in use.
    Am I missing the point by saying;
    the liquid alcohol is burnt, therefore evaporates producing a gas which is lost, so the mass decreases??? :confused:
    • Community Assistant
    • Study Helper

    Community Assistant
    Study Helper
    yes, it says "even when not in use" therefore it isn't burning...

    however you are correct in that the reason is evaporation of the volatile spirits in the burner..

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