Quiz question #7

Volume: $\Delta S = nR\ln \frac{V_{2}}{V_{1}}$
Temperature: $\Delta S = nC\ln \frac{T_{2}}{T_{1}}$

Diana_OToole_1F
Posts: 10
Joined: Fri Jan 08, 2016 3:00 am

Quiz question #7

On the practice quiz it's asking which of the list of processes leads to an increase in entropy and I don't understand why "5) A glass of water loses 100J of energy reversibly at 30ºC" doesn't lead to an increase in entropy. If it's a reversible process and the temperature is constant, more work is being done so shouldn't that also mean the entropy increases because heat is entering the system and resulting in an entropy change?

Xinyi_Yan_3L
Posts: 21
Joined: Wed Sep 21, 2016 2:56 pm

Re: Quiz question #7

Actually this process leads to an decrease in entropy. For an isothermal process, ΔG=q(reversible)/T
Clearly, since the system (the glass of water) is losing heat, q is negative Thus ΔG is also negative, which means decrease in entropy.