calcium oxide calcium oxide calcium oxide (c) In an attempt to determine AHcombu

Question

calcium oxide calcium oxide calcium oxide (c) In an attempt to determine AHcombustion of lauric acid experimentally, a student places a 1.5 g sample of lauric acid in a ceramic dish underneath a can made of Al containing 325 g of water at 25°C. The student ignites the sample of lauric acid with a match and records the highest temperature reached by the water in the can. (6) The experiment is repeated using a can of the same mass, but this time the can is made of Cu. The specific heat of Cu is 0.39(g:K), and the specific heat of Al is 0.90Jg K). Will the final temperature of the water in the can made of Cu be greater than, less than, or equal to the final temperature of the water in the can made of Al? Justify your answer. (ii) In both experiments it was observed that the measured final temperature of the water was less than the final temperature calculated in part (b). Identify one source of experimental error that might account for this discrepancy and explain why the error would make the measured final temperature of the water lower than predicted.

Explanation / Answer

i) Specific heat indicates the quantity of heat required to raise the temperature of unit mass of substance by unit Kelvin. So when the can is made of Copper,which has lower specific heat,the same quantity of heat liberated will result in higher temperature rise of can and subsequently water, as compared to when can used is of Aluminium.

ii) Generally, the calculated values of temperature indicate a case where the entire heat transfer takes place from lauric acid sample to can and then to water whereas in actual case,there are heat losses to surroundings due to which the temperature rise observed is not same as calculated.

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