plz help How much does the internal energy of 5 g of ice at 0 degree C increase

Question

plz help

How much does the internal energy of 5 g of ice at 0 degree C increase as it is changed to water at 0 degree C? Neglect the small change in volume. [c = 1 cal/g. degree C, L = 80 cal/g and 1 cal = 4.184 J/cal] 400 J 600 J 1670 J 1760 J 2000 J Compute the maximum possible efficiency of a heat engine operating between the temperature limits of 100 degree C and 400 degree C. 10% 20% 35% 45% 55% Twenty grams of ice at 0 degree C melts to water at 0 degree C. How much does the entropy of the 20 g change in this process? [Use information given above] 24.5 J/K 400 J/K 600 J/K 40.5 J/K 60.5 J/K

Explanation / Answer

Q6

change in internal energy = mass * L = 5 * 80 = 400 Cal = 400 * 4.184 J = 1673.6 J =--- opition c)

Q7

T_high = 400 Celcius = 400 + 273 = 673 K
T_low = 100 Celcius = 100 + 273 = 373 K

so effeciency = 1 - ( T_low/ T_high ) = 1 - ( 373/673 ) = 0.4457652 = 45 % -- option d)

Q8

entropy = heat / temp
temp = 0 C = 273 K

Heat = 20 * 80 * 4.184 = 6694.4J

so change in entropy = 6694.4 / 273 = 24.5 J / K   -- option a

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