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
thanks
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. 
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.
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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
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