Question

Which of the following aqueous solutions are good buffer systems?
.
0.21 M hydrofluoric acid + 0.13 M hydrobromic acid.
0.35 M calcium iodide + 0.23 M sodium iodide.
0.27 M ammonia + 0.36 M ammonium bromide.
0.20 M hydroiodic acid + 0.15 M potassium iodide.
0.14 M barium hydroxide + 0.22 M barium bromide.

Answer 1

A buffer is a water-based solution containing a mixture of either an acid and its conjugate base, or a base and its conjugate acid. The acids and bases used in a buffer are quite weak and when a small amount of a strong acid or base is added, the pH doesn't change significantly.

In the question

First option doesn’t contain any acid.- so not a buffer

Second one doesn’t contain any base--- hence not a buffer

Third option is a buffer.

4^th option contains strong acid---- ( not a buffer)

5^th option contains strong base ----- ( not a buffer)

So the answer for the buffer is third option that is

0.27 M ammonia + 0.36 M ammonium bromide. [ weak base and its conjugate acid]