5: An iron block of unknown mass at 79 C is dropped into an insulated tank that contains 151 L of water at 22 C. At the same time, a paddle wheel driven by 257 W motor is activated to stir water. It is observed that thermal equilibrium is established after 17 minutes with a final temperature of 28 C. Assume the surrounding temperature is 18 C. The density and specific heat of water at 25°C are p-997 kg/m² and c-4.18 kJ/kgC. The specific heat of iron at room temperature is c, 0.45 kJ/kgC. a. Determine the mass of the iron block. b. Determine the exergy destroyed during the process.

5: An iron block of unknown mass at 79 C is dropped into an insulated tank that contains 151 L of water at 22 C. At the same time, a paddle wheel driven by 257 W motor is activated to stir water. It is observed that thermal equilibrium is established after 17 minutes with a final temperature of 28 C. Assume the surrounding temperature is 18 C. The density and specific heat of water at 25°C are p-997 kg/m² and c-4.18 kJ/kgC. The specific heat of iron at room temperature is c, 0.45 kJ/kgC. a. Determine the mass of the iron block. b. Determine the exergy destroyed during the process.