Question

A rigid tank is divided into two equal parts by a partition. One part of the tank contains 1.5 kg of compressed liquid water at 300 kPa and 60 degree C while the other part is evacuated. The partition is now removed, and the water expands to fill the entire tank. Determine the entropy change of water during this process, if the final pressure in the tank is 15 kPa.

Answer 1

In this case, the entropy change of water during the expansion process is -6403 J/K.

Step-by-step explanation:

The entropy change of water during the expansion process can be determined by calculating the entropy change of the system. In this case, the system consists of the compressed liquid water in one part of the tank before the partition is removed, and the expanded water filling the entire tank after the partition is removed.

The entropy change of the system can be calculated using the formula: ΔS = mc∆T / T, where ΔS is the entropy change, m is the mass of the water, c is the specific heat capacity of water, and ∆T is the change in temperature.

Step 1: Calculate the change in temperature (∆T) by subtracting the final temperature (60 ℃) from the initial temperature (300 ℃).

∆T = 60 ℃ - 300 ℃ = -240 ℃

Step 2: Calculate the entropy change (ΔS):

ΔS = (1.5 kg)(4190 J/kg∙K)(-240 ℃) / (60 ℃ + 273.15 K) = -6403 J/K

Therefore, the entropy change of water during the expansion process is -6403 J/K.