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# Weak acid and strong base? watch

1. The general equation is:
HA + OH- -----> A- + H2O

But what about when there is 2OH- e.g. Ba(OH)2
Is it:
2HA + 2OH- -----> 2A- + 2H2O

But when i use this to work out pH for a weak acid and strong base it doesnt work.

E.g. Find pH when 50cm3 0.5moldm-3 chloroethanoic acid is added to 25cm3 0.1moldm-3 Ba(OH)2

If you multiply A- and HA by 2 the answer is wrong
2. You just use the general equation, but note that every mol of Ba(OH)2 produces 2 mol of OH-.
3. (Original post by Pigster)
You just use the general equation, but note that every mol of Ba(OH)2 produces 2 mol of OH-.
Like this?:
HA + 2OH- -----> A- + H2O

But that doesnt balance
4. (Original post by kiiten)
Like this?:
HA + 2OH- -----> A- + H2O

But that doesnt balance
Nope.

Imagine adding 1 mol of Ba(OH)2 (containing 2 mol of OH-) to 10 mol of HA (able to form 10 mol of H+).

8 mol of HA would remain and 2 mol of A- would form.

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