Liquid nitrogen is stored in a Dewar flask at a temperature T1 = 78°K in an amount of 2 liters. Half of this amount evaporated within a day. Determine the specific heat of evaporation of nitrogen if it is known that 40 g of ice in the same dewar will melt within 22 hours 30 minutes. The rate of heat supply inside the dewar can be considered proportional to the temperature difference between inside and outside the dewar. Ambient air temperature T = 293° K. The density of liquid nitrogen at 78° K is 800 kg/m3.

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