A boulder of mass 2000. kg breaks loose of a mountainside and plunges 200. m straight down into a lake at a temperature of 5.00◦C. Assuming the energy of the rock transforms into thermal energy, calculate the change in entropy of the lake.

DS = 13865.7[J/K]

Explanation:

We can calculate the energy of the rock, like the potential energy relative to the lake level. Which can be calculated by means of the following expression of the potential energy:

Therefore:

This energy is transformed into thermal energy.

we shall remember that isothermal heat transfer processes are internally reversible, so the entropy change of a system during one of these processes can be determined, by the following expression.

T = 5 + 278 = 283[K]

DS = 3924000 / 283

DS = 13865.7[J/K]

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