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pH of compounds

Mutleybm1996

Hi everyone,
Is there a way of determining the pH of compounds? For instance a question from the 2007 F321 exam says 'suggest a value of the pH of lime water'

Any ideas?

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Reply 1

Solivagant

Well you should know that lime water is calcium hydroxide solution. You know that lime water is murky, and this is to do with the fact that some of the calcium hydroxide remains, and doesn't dissociate. But it has the formula Ca(OH)2, and is a strong base, so I'd assume around 11-13, but I'm just estimating :dontknow:

Reply 2

davidtyoember

Original post by benwalters1996

Hi everyone,
Is there a way of determining the pH of compounds? For instance a question from the 2007 F321 exam says 'suggest a value of the pH of lime water'

Any ideas?

Posted from TSR Mobile

#

You would need to determine the concentration of OH- ions in the solution since im assuming its alkaline then from there you would need to use the equation : pH = 14 -pOH

pOH = -log[concentration of OH]

Reply 3

Borek

No such thing as "pH of compound". pH is a property of the solution.

Solubility of lime is around 0.023 M (1.7 g/L) at room temperature, and - even if it is quite a strong base - it is not 100% dissociated. My calculations suggest pH around 12.2. Assuming full dissociation you would get around 12.6 (both comparable with CJG21's estimate).

Reply 4

Plantagenet Crown

If the question is that vague I would assume a basic knowledge of whether the aqueous solution is acidic or alkaline as well as the appropriate pH values is needed.

Reply 5

davidtyoember

Original post by Plantagenet Crown

If the question is that vague I would assume a basic knowledge of whether the aqueous solution is acidic or alkaline as well as the appropriate pH values is needed.