# How much acid and base do you combine to make a ph7 liquid, given you know the 2 ph

1. Jul 20, 2010

### perd1t1on

Hello. This is probably a really dumb question, but I was wondering how the ph system works in relation to making a ph 7 liquid (which would be water and salt, right?)

The way I was thinking was if you have an acid with a ph3 and a base with a ph8, and you wanted to mix them to produce a ph7 liquid, you would have to do it proportionally:

7*2 = 14 = 8x + 3y = 8(1) + 3(2)
x = 1, y = 2
1 part base, 2 parts acid.

If this is not how it's done, is there a simple way to do it (aka given you have the ph of both the acid and base, what is the ratio to make a ph7 liquid?). This is not a homework question and I'm not a chemist.

2. Jul 21, 2010

### Sakha

Re: How much acid and base do you combine to make a ph7 liquid, given you know the 2

As far as I know pH is a logarithmic unit, so a pH of 3 has 105 more H+ ions than a pH of 8. If I'm correct then your simple algebra wouldn't work. It would work if you do it directly with the H+ concentration instead of pH, and also taking in account for the total volume.

Last edited: Jul 21, 2010