In 1-3 sentences, critically evaluate each of the following statements, stating
ID: 1071480 • Letter: I
Question
In 1-3 sentences, critically evaluate each of the following statements, stating whether the conclusion is reasonable or violates basic principles of thermodynamics. A sample of air is separated from a large evacuated chamber and the entire system is isolated from the surroundings. A small pinhole between the two chambers is opened and roughly half the gas is allowed to effuse into the second chamber before the pinhole is closed. Because nitrogen effuses faster than oxygen, the gas in the second chamber is richer in nitrogen, and that in the first chamber is richer in oxygen than the original air. The gases have thus at least partially spontaneously unmixed, which is a violation of the Second Law. One can supercool water and maintain it at temperatures as low as -10 degree C. A sample of supercooled liquid water is isolated in a closed, thermally insulated container. After a time the water spontaneously changes to a mixture of ice and water at 0 degree C. The spontaneous increase in the water's temperature with no heat input from the surroundings is consistent with the Second Law. A volume of an aqueous solution of hydrogen peroxide is placed in a cylinder and covered with a tight-fitting piston. TA small amount of the enzyme catalase is placed on a probe and introduced into to the solution. The enzyme catalyzes the decomposition of the hydrogen peroxide, and the decomposition products raise the piston. The catalase is then withdrawn, allowing the hydrogen peroxide to reform and the piston returns to its original position. By connecting the piston to an engine, net work can be obtained indefinitely by cyclically inserting and removing the catalase.Explanation / Answer
(a.) Effusion creates an "Unmixing" phenomenon, and it can be observed that the gases are expanding into a larger volume. Thus, a large increase in entropy is acheived. Thus, the 2nd law is not actually violated.
(b.) Yes. This phenomenon is totally consistent with all thermodynamic laws. On conversion of supercooled water at low temperature to partially water & ice at higher temperature, is a phenomenon with a net Increase in the entropy. Infact, the fraction of water and ice formed, can be calculated using the expression of 2nd law.
Freezing of supercooled water and subsequent increase in temp.is an irreversible process. Stotal (=Qrev/T) value is always POSITIVE for this process at temperatures below 273K.
(c.) No. It is impossible to indefinitely obtain a net work to run an engine. This violates the 2nd law of thermodynamics. The entropy of the universe will never decrease. If we consider one rotation of the cycle, i.e. one rise and fall of the piston, the entropy change for this process isn't zero. Thus, the engine will not work indefinitely. It has to stop after some time, if no external work/energy is involved.