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Chem 3B Jan 04 question. watch

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    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:
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    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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