Flashcards in Determination of enthalpy change of combustion Deck (7)
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1
first step for determination of /\HC of methanol?
1) using a measuring cyliner, measure out 150 cm^3 of water, pour water into beaker, record initial temp. of water to the NEAREST 0.5 degrees c,
2
2nd step
2) add methanol to spirit burner, weigh spirit burner containing the methanol
3
3rd step
3) place spirit burner under the beaker with clamp holding beaker and thermometer in beaker.
4
4th step
4) after 3 mins extinguish flame and immediately record max. temp reached by the water
5
5th step
5) re-weigh the spirit burner containing methanol and assume that the wick has not been burnt
6
how may the experimental enthalpy change of combustion value be inaccurate?
-heat loss to surroundings other than water, (includes beaker but mainly air surrounding)
-incomplete comb. of methanol (CO and C being produced instead of CO2)
-evaporation of methanol from the wick (therefore burner should be weighed as soon as possible after extinguishing the flame spirit burners usually hve a cover to reduce error)
- non-standard conditions.
7
