A 4-kg mass of metal of unknown specific heat at a temperature of 600 degree C i
ID: 1623037 • Letter: A
Question
A 4-kg mass of metal of unknown specific heat at a temperature of 600 degree C is dropped into 0.5 kg of ice and 0.5 kg of water both at 0 degree C. With no heat losses to the surroundings, the equilibrium temperature of the mixture is 85 degree C. Calculate the specific heat of the metal. A) 0.04 kcal/kg degree C B) 0.06 kcal/kg degree C C) 0.08 kcal/kg degree C D) 1.6 kcal/kg degree C E) 1.2 kcal/kg degree C Suppose you do 75 kJ of work on a system consisting of 10 kg of water by stirring it with a paddle wheel. During this process, 40 kcal of heat is removed. the change in the internal energy of the system is A) -35 kJ B) -115 kJ C) -134kJ D) -242kJ E) -156 kJExplanation / Answer
9)
Mass(metal) = 4 kg
Tm = 600C
Specific heat of water = 4186 j/kgC
Specific heat of Ice = 2000 j/kgC
Specific heat of Metal = Sm J/kg/C
Energy balance:
4xSx(600-85) = 0.5x4186x(85-0) +0.5x2000x(85-0)
2060S = 177905 + 85000
Sm = 127.62 j/kgC
10)
As per the first law of thermodynamics:
Q = W + U
U = increase in Internal energy
W = work done = 75 KJ
Q = heat = 167.36 KJ
U = Q - W
Work done on the system is negative hense W = - 75 KJ
= -242 KJ