Conjugates of each other, but used to prepare buffer

Question

i. NaOH and HCl

ii. HF and NaF

iii. NH3 and HCl

iv. C2H5NH2 and C2H5NH3Cl

v. NH3 and KOH

vi. NaOH and HCN

Answer 1

Steve O is correct and in addiition NaOH reactas with HCN to produce the CN^-1 conjugate base so you would have both present. Also NH3 and HCl reacted together will produce NH4+ the acid conjugate of NH3.......so pure answer strict interpretation of the Q ..as SAteve O said ...any grey area on interpreting formation of a conjugate ..then all but i.  fit the bill

Answer 2

ii. HF and NaF

iv. C2H5NH2 and C2H5NH3Cl

are conjugates of each other, but used to prepare buffer

======================

as an edit to address Merlin's contribution:,

I know what you are saying.

He asked this question through two  separate postings .

This question asks which of the choices, have "conjugate pairs" being mixed to make a buffer

---------------

What you are refering to, he asked in his first question posted @:

http://answers.yahoo.com/question/index?...

There he asked which of the same choices, would make a buffer, eventhough you are not mixing conjugate pairs...

On this other question I also chose the other two buffers that you refer to, where a set conjugate pairs is being produced, by  the mixing of non-conjugate  acid & base.

I also chose iii. NH3 and HCl & vi. NaOH and HCN  to answer this other  question.

------------------------------

however we all know that mixing two bases as in v. NH3 and KOH , won't make a buffer.

& we know that  neither will mixing a strong acid with a strong base as in i. NaOH and HCl