A hot 10 kg block of iron initially at 500 oC is dropped into an insulated tank

ID: 2994669 • Letter: A

Question

A hot 10 kg block of iron initially at 500 oC is dropped into an insulated tank that

contains 50 kg of liquid water. The final equilibrium temperature of the water and

iron is measured to be 25oC. A paddle wheel is used to stir the water and transfers 500

kJ of energy to the water during this process. The water and iron specific heats may

be assumed to be CH2O = 4180 J/kg.oC and Ciron = 447 J/kg.oC. Determine the initial

temperature of the water and determine the amount of heat transfer from the iron

block to the water.

Mass of iron block, m1 = 10 kg

Mass of water, m2 = 50 kg

Initial temperature of Iron block, Ti = 500 deg

Final Temperature of Iron block,Tf = 25 deg

Final Temperature of water,Tf = 25 deg

Initial temperature of water, Tw = ?

Work done = 500 kJ

m2*Cpw*(Tf - Tw) = m1*Cp*(500-25) + 500*10^3

50*4180*(25-Tw) = 10*447*(500-25) + 500*1000

Tw = 12.4485 deg

heat lost by Iron,Q = m1*Cp*(Tf - Ti) = 10*447*(25-500) = -2123250 J

Heat Transfer from the Iron block to the water is = -Q = 2123250 J = 2123.25 kJ

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