## A 50-kg iron block and a 20-kg copper block, both initially at 80°C, are dropped into a large lake at 15°C. Thermal equilibrium is establish

Question

A 50-kg iron block and a 20-kg copper block, both initially at 80°C, are dropped into a large lake at 15°C. Thermal equilibrium is established after a while as a result of heat transfer between the blocks and the lake water. Assuming the surroundings to be at 20°C, determine the amount of work that could have been produced if the entire process were executed in a reversible manner.

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3 years 2021-08-28T17:24:45+00:00 1 Answers 440 views 0

## Answers ( )

The amount of work produced by the entire process of cooling the iron and the copper is 1969.5 kJ

Explanation:

Given;

mass of iron = 50 kg

mass of copper = 20 kg

initial temperature of iron and copper = 80 °C

temperature of the lake = 15°C

Both iron and copper forms a closed system and attained thermal equilibrium.

This energy balance can be expressed as;

Net heat transfer = change in internal energy

Δ = Δ + Δ

And U = McΔT

C is specific heat capacity; ( iron = 0.45 kJ/kg.K, copper = 0.39 kJ/kg.K)

ΔU = 50 x 0.45 (80 -15) +  20 x 0.39 (80 -15)

ΔU = 1462.5 kJ + 507 kJ = 1969.5 kJ

The amount of work produced by the entire process of cooling the iron and the copper is 1969.5 kJ