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# How to make solutions of specific pH watch

1. So I want to make solutions of pH 6.8, 6.9, 7.0, 7.1, 7.2, 7.3, 7.4, 7.5 7.6, 7.7 and 7.8

I have 50cm3 of (let's say) pure, pH 7.0 water.
How much HCl or NaOH of concentration 1x10^-7 do I need to add to make each solution?

I'm doing some simple calculations but none of them seem to work out.
2. (Original post by BI0)
So I want to make solutions of pH 6.8, 6.9, 7.0, 7.1, 7.2, 7.3, 7.4, 7.5 7.6, 7.7 and 7.8

I have 50cm3 of (let's say) pure, pH 7.0 water.
How much HCl or NaOH of concentration 1x10^-7 do I need to add to make each solution?

I'm doing some simple calculations but none of them seem to work out.
Use pH to work out [H+] and from this calculate the number of moles of acid per litre.

Use this to find how many moles of acid you have to add.

Then using your acid concentration find out what volume of acid contains this number of moles.

Although, if you are only given acid and base of concentration 1 x 10-7 M it is simply not possible to change the pH of water, as water already contains [H+] and [OH-] of this concentration.
3. (Original post by charco)
Use pH to work out [H+] and from this calculate the number of moles of acid per litre.

Use this to find how many moles of acid you have to add.

Then using your acid concentration find out what volume of acid contains this number of moles.

Although, if you are only given acid and base of concentration 1 x 10-7 M it is simply not possible to change the pH of water, as water already contains [H+] and [OH-] of this concentration.

Alrigth, I'll change the conc to 10^-4 mol dm^-3.

I don't understand how I can work out the number of moles of acid I need to add when I don't know the volume?
4. (Original post by BI0)
Alrigth, I'll change the conc to 10^-4 mol dm^-3.

I don't understand how I can work out the number of moles of acid I need to add when I don't know the volume?
... assume there is one litre
6. (Original post by alow)
Could be studying International History and Politics ...

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