pH and stuff

[doter]

hey guys
i really dont understand all the pH questions when they ask for example
that a solution was diluted or a base or acid was added, what happens to the ph?
does anyone have any general tips on pH questions?
thanks in advance!!

[Andiio]

pH is basically an indicator of the acidity or converse basicity of a solution.

a pH of 7 is neutral - the equilibrium; a good example of a solution with pH 7 would be water.

If the pH of a solution is <7, then it is said to be acidic.
If the pH of a solution is >7, then it is said to be basic.

Thus, if a solution is diluted, then it is getting less acidic - thus the pH of the solution INCREASES.

[98.40_for_sure]

You're going to have to discard all that year 7-10 science knowledge about pH < 7 = acid, pH > 7 = base and shiz.
The purest definition of pH is that it is a measure of H+ ions, it has no relation to OH-.
Acidity and basicity is dependent on the proportion of H+ ions to OH- ions, it has nothing to do with pH.

[Mao]

You're going to have to discard all that year 7-10 science knowledge about pH < 7 = acid, pH > 7 = base and shiz.
The purest definition of pH is that it is a measure of H+ ions, it has no relation to OH-.
Acidity and basicity is dependent on the proportion of H+ ions to OH- ions, it has nothing to do with pH.

partially true. But since when did H+ not have a relation to OH-?

[98.40_for_sure]

You're going to have to discard all that year 7-10 science knowledge about pH < 7 = acid, pH > 7 = base and shiz.
The purest definition of pH is that it is a measure of H+ ions, it has no relation to OH-.
Acidity and basicity is dependent on the proportion of H+ ions to OH- ions, it has nothing to do with pH.

What about pH = - log [H+]? Most technical definition

Thats exactly what i said... look ^ bold

[physics]

SORRY to BUTT IN but i have a question =D

well i got caught by the weak acid getting diluted and the strong acid getting diluted:P

apparently if u dilute soomethin by a factor of 10 the ph increases by 1 but
weak acids would not increase by 1 but less than 1
strong acids would get increased by 1

is this due to ionisation? and how weak acids dont ionised as much as strong acids?

and what would happen if the weak acid was present in HIGH concentrations? it'll still ionise less than a strong acid with a low con/c?

[Martoman]

Defs.

Its like this. Discounting tactics, terrain and other factors think of it like this.

You have a weak army vs a strong army millions of times stronger. If they have equal numbers, the strong army will always beat the weaker one.

If you increase the size of the weak army, whilst it will put up a very dismal fight, the stronger army will beat them, always.

what im getting at here is that whilst you can increase the concentration of a weak acid, it will never ionise more than a strong one.

If you increase the concentration sure more will be ionised, but not to a massive extent.

If you dilute a weak acid the ionisation increases but the concentration decreases.

Yet for a strong acid, it will ionise essentially fully and diluting it will decrease the ceoncentration of the acid.


The underlying reason behind this is that weak acids conjugate are stronger bases, the base will want to mop up a lot of the ions being sent out. This means the back reaction is favoured far more than the forward.