Question

How many grams of coffee must evaporate from 350 g of coffee in a 100-g glass cup to cool the coffee from 95.0ºC to 45.0ºC? You may assume the coffee has the same thermal properties as water and that the average heat of vaporization is 2340 kJ/kg (560 cal/g). (You may neglect the change in mass of the coffee as it cools, which will give you an answer that is slightly larger tha

Answer 1

Answer:

33 gm.

Explanation:

Heat required by coffee in evaporation = m L = m x 560 cals

Heat released by coffee in cooling = m c Δ T = 350 X 1 X 50 = 17500 cals

Heat released by glass cup = 100 x .2 x 50 = 1000 cals ( specific heat of glass is .2 cals per gram per k)

Total heat released = 18500 cals

Heat gained = heat lost

m x 560 = 18500

m = 33 gm.