## pH and van’t hoff

$\ln K = -\frac{\Delta H^{\circ}}{RT} + \frac{\Delta S^{\circ}}{R}$

Marsenne Cabral 1A
Posts: 59
Joined: Fri Sep 28, 2018 12:19 am

### pH and van’t hoff

why would the neutral ph change from 7 in a chemical reaction and how is that possible?

Ashley Kim
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Joined: Fri Sep 28, 2018 12:19 am
Been upvoted: 1 time

### Re: pH and van’t hoff

The neutral pH can change with temperature, because pH is not constant with temperature.

Kathryn Wilhem 1I
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Joined: Fri Sep 28, 2018 12:27 am

### Re: pH and van’t hoff

With a temperature change, the K changes, so then the pH would also change because the concentration of H+ changes.

Joonsoo Kim 4L
Posts: 61
Joined: Fri Sep 28, 2018 12:29 am

### Re: pH and van’t hoff

When temperature increases, the Kw increases as well, which causes the neutral [H+] to increase and neutral pH to decrease. On the flip side, when temperature decreases, the Kw and neutral [H+] decrease, so the neutral pH increases. Neutral pH of 7 is only true at 298K.

Yvonne Du
Posts: 64
Joined: Fri Sep 28, 2018 12:23 am

### Re: pH and van’t hoff

Joonsoo Kim 4L wrote:When temperature increases, the Kw increases as well, which causes the neutral [H+] to increase and neutral pH to decrease. On the flip side, when temperature decreases, the Kw and neutral [H+] decrease, so the neutral pH increases. Neutral pH of 7 is only true at 298K.

Thank you this is very helpful!

Jonathan Christie 1I
Posts: 32
Joined: Mon Apr 09, 2018 1:38 pm

### Re: pH and van’t hoff

Thank you, this was a big help in figuring out where I went wrong on the Vant Hoff problem on test 2

Roberto Gonzalez 1L
Posts: 39
Joined: Fri Sep 28, 2018 12:17 am

### Re: pH and van’t hoff

A neutral pH of 7 is only true for water at 25 degrees celsius. As the temperature changes, Kw changes and therefore as [h30+] is calculated by taking the square root of Kw, the neutral pH value will differ accordingly.