Asolution containing which one of the following pairs of substances will be a buffer solution?
a) rbcl, hcl
b) kbr, hbr
c) csf, hf
d) nai, hi
e) none of the above

CsF, HF

Explanation:

A buffer is a solution of a weak acid and its salt. Of all the halogen acids listed in the options HF is the weakest acid because the HF bond is difficult to break hence HF does not ionize to a large extent. Its pKa is about 3.1. All other halogen acids listed are strong acids and cannot be used as buffers.

Hence a solution of HF and CsF can function as a buffer solution.

so here we go

atomic mass

239 + 1 = y + 134 + 3 combine like terms

240 = y + 137             subtract 137 from both terms

240 - 137 = y

103 = y

atomic number

94 = z +54 + 0

94 = z + 54               subtract 54 from both sides.

40 = z

answer