Question

Which of the following result in buffered solutions when equal volumes of the two solutions are mixed?

a.) .1 M HCl and .1 M NH4Cl
b) .1 M HCl and .1 M NH3
c.) .2 HCl and .1 M NH3
d.) .1 M HCl and .2 M NH3

By def. I know that a buffed solution is made from a weak base and it's conjugate acid/or a weak acid and it's conjugate base. Therefore, I don't really understand how to determine the answer since each option includes a strong acid.

Answer 1

A little confusing, perhaps, but answerable.
Isn't a "REAL" buffered solution present in d? (Just as you described it in your question.)
..........HCl + NH3 ==> NH4Cl
I.........0.1M..0.2M......0
C........-0.1..-0.1......+0.1
E..........0.....0.1.......0.1

So you end up with NH3, a weak base, with it's conjugate acid, NH4^+. Voila.