You are Here: Home

# pH 7 - why? watch

1. At 25 oC, pH = 7.00 since at that temperature, [H+] = 1.00 x 10-7 mol dm-3.

Why is the concentration such a nice round number? Coincidence or something I'm overlooking that I'm about to kick myself for?
2. Oh yes.. I've been doing this today in chemistry, or I might just tell you anyway..

May I ask what level you are studying chemsitry before I delve deep into discussion?
3. (Original post by BDunlop)
May I ask what level you are studying chemsitry before I delve deep into discussion?
I did first year chemistry at university about 25 years ago.
4. The ionic product of water is 1x10^-14 at room temp. I mean I guess it's not going to be exactly exactly, probably 0.00000009876...moldm^-3 or something. It's so close to 1x!0^-7 though that it's a fine baseline and depending on v small temp differences I'm sure it would get incrementally close and further way from 1x10^-7.
5. (Original post by Pigster)
At 25 oC, pH = 7.00 since at that temperature, [H+] = 1.00 x 10-7 mol dm-3.

Why is the concentration such a nice round number? Coincidence or something I'm overlooking that I'm about to kick myself for?
Apparently its "true" value is 0.991 x 10-14 at 298K

http://www1.lsbu.ac.uk/water/water_dissociation.html
6. (Original post by charco)
Apparently its "true" value is 0.991 x 10-14 at 298K
Chemguide states it as 1.008 x 10-14 - go figure.
7. It has to be something to some amount of significant figures I suppose.

Unless it's one of those things like at the end of Carl Sagan's 'Contact'.

### Related university courses

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: October 30, 2017
Today on TSR

### Results day under a month away

How are you feeling?