A vessel of water equivalent 100 g contains 900 g water at 30°C. Evaporation is 1 g/s; lv = 500 cal/g, cw = 1 cal/(g °C). Include mass loss and ignore other heat transfer. Time for 5°C cooling, to thr

Question

A vessel of water equivalent 100 g contains 900 g water at 30°C. Evaporation is 1 g/s; lv = 500 cal/g, cw = 1 cal/(g °C). Include mass loss and ignore other heat transfer. Time for 5°C cooling, to three decimals in s?

TestHub · Accepted Answer

Heat capacity = 1000 − t cal/K. Thus d t d T ​ = − ( 1000 − t ) 500 ​ . Integrating gives 5 = 500 ln [ ( 1000 − t ) 1000 ​ ] , hence t = 1000 ( 1 − e − 0.01 ) = 9.950166 s .

Physics - Heat & Thermo Question with Solution | TestHub

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