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Solved: To heat 1 cup of water to make coffee,
Chapter 20, Problem 62P(choose chapter or problem)
To heat 1 cup of water \(\left(250 \mathrm{~cm}^3\right)\) to make coffee, you place an electric heating element in the cup. As the water temperature increases from \(20^{\circ} \mathrm{C}\) to \(78^{\circ} \mathrm{C}\), the temperature of the heating element remains at a constant \(120^{\circ} \mathrm{C}\). Calculate the change in entropy of (a) the water; (b) the heating element; (c) the system of water and heating element. (Make the same assumption about the specific heat of water as in Example 20.10 in Section 20.7, and ignore the heat that flows into the ceramic coffee cup itself.) (d) Is this process reversible or irreversible? Explain.
Questions & Answers
QUESTION:
To heat 1 cup of water \(\left(250 \mathrm{~cm}^3\right)\) to make coffee, you place an electric heating element in the cup. As the water temperature increases from \(20^{\circ} \mathrm{C}\) to \(78^{\circ} \mathrm{C}\), the temperature of the heating element remains at a constant \(120^{\circ} \mathrm{C}\). Calculate the change in entropy of (a) the water; (b) the heating element; (c) the system of water and heating element. (Make the same assumption about the specific heat of water as in Example 20.10 in Section 20.7, and ignore the heat that flows into the ceramic coffee cup itself.) (d) Is this process reversible or irreversible? Explain.
ANSWER:Step 1 of 4
This process involves the change in entropy. As we know that entropy is defined as the number of ways a system can be arranged. The higher the entropy more the system is disordered.If the process is reversible ,then the change in entropy is equal to the heat absorbed divided by the temperature of the reversible process. In the equation, Q is the heat absorbed, T is the temperature and S is the Entropy.
This process involves irreversible heat flow because of the temperature heat flow.
= (4190
-k)
=(4190)(In(
))=756.77J/K
=(4190
)(In(
))=758.561J/K