Solutions ph volume

can anyone explain this please
which one of the following solutions reacts with an equal volume of 0,05M Ba(OH)2 giving a pH=7 solutions?
a)0,1 M HClO4
b)0,1M KCl
c)0,1M NH3
d)0,1M CH3OH
e)0,1M NaOH
the answer is a

You have hydroxyl ions in your solution due to dissociation of Ba(OH)2. These ions must be neutralized by an acid to get a pH=7. The only acid in the options is HClO4. No need to make calculations in this case. :slightly_smiling_face:

But for good sake, we can check. We can write the reaction and balance it:
Ba(OH)2 + 2HClO4 → Ba(ClO4)2 + 2H2O

Reactants ratio is 1:2 moles. It means we must use double koncentration than 0.05 M, if we must use the same volume of our choice. Checking that confirms that our HClO4 has a concentration of 0.1 M.


ba(oh)2 is a base
you want a solution with ph 7 which means you want a salt
a reaction between acid and base gives you salt so you need to find in the options below which is acid,which is option a
kcl is salt
nh3 base,ch3oh and naoh are bases
so correct option is a