## Gas vs solid

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

Jennifer Guzman 4C
Posts: 38
Joined: Wed Feb 14, 2018 3:01 am

### Gas vs solid

Why is the entropy of a gas in an aqueous solution less than the entropy of a solid in an aquesous solution?

Brandon_Tran_2E
Posts: 63
Joined: Fri Sep 28, 2018 12:23 am

### Re: Gas vs solid

Think of entropy as disorder, gas molecules and more dispersed and disordered in an aqueous solution whereas a solid is a literal solid and ordered.

kimberlyrose1G
Posts: 44
Joined: Fri Sep 28, 2018 12:27 am

### Re: Gas vs solid

Jennifer Guzman 4C wrote:Why is the entropy of a gas in an aqueous solution less than the entropy of a solid in an aqueous solution?

To answer your question piggybacking off of the previous reply, entropy should increase as you go from solid to liquid to gas. Therefore the entropy of gas should be more than the entropy of a solid (because it occupies more volume).

harshitasarambale4I
Posts: 58
Joined: Fri Sep 28, 2018 12:26 am

### Re: Gas vs solid

Is this why delta U = delta H in biological systems since reactions in biological systems take place in liquids?

Timothy_Yueh_4L
Posts: 57
Joined: Fri Sep 28, 2018 12:28 am

### Re: Gas vs solid

harshitasarambale4I wrote:Is this why delta U = delta H in biological systems since reactions in biological systems take place in liquids?

The reason why delta U = delta H in biological systems is because these reactions usually occur in aqueous solutions, which unlike gas is unable to expand or compress to perform work. Therefore the work done by compress/expansion doesn't apply to these biological systems and the total energy of the system is equal to delta H.

katie_sutton1B
Posts: 61
Joined: Fri Sep 28, 2018 12:17 am

### Re: Gas vs solid

Since a solid is compact and the molecules do not move, it has less entropy. Since gas molecules are very spread out, they have more disorder and therefore more entropy.