.1 M HCl + .1 M NaCl

.1 M HF + .1 M NaF
.1 M HBr + .1 M NaBr

Which of the above would be considered buffers?

A buffer is a mixture of a weak acid and one of its salts OR a weak base and one of its salts.

HCl is a strong acid.
HBr is a strong acid.
How can you tell if an acid is a weak one or a strong one. Look in the back of your text for ionization constants. If it is listed, it is a weak acid (or base). If it isn't listed, chances are good it is strong. There is another way, also. The common strong acids are
HCl
HBr
HI
HNO3
HClO4
HClO3
There are three or four more but they aren't common.
H2SO4 (only the first H is strong).

To determine whether a solution is a buffer, you need to check if it consists of a weak acid and its conjugate base (or a weak base and its conjugate acid) at appreciable concentrations.

Let's analyze each of the given solutions:

1. 0.1 M HCl + 0.1 M NaCl:
HCl is a strong acid, and NaCl is its corresponding salt. Since HCl is a strong acid, it completely dissociates into H+ and Cl- ions. Therefore, this solution does not contain a significant concentration of the weak acid and its conjugate base, so it is not a buffer.

2. 0.1 M HF + 0.1 M NaF:
HF is a weak acid, and NaF is its corresponding salt. HF only partially dissociates into H+ and F- ions. Since HF is a weak acid and NaF provides a source of F- ions, this solution can be considered a buffer. It contains both the weak acid (HF) and its conjugate base (F-) at appreciable concentrations.

3. 0.1 M HBr + 0.1 M NaBr:
HBr is a strong acid, and NaBr is its corresponding salt. Similar to the first case, since HBr is a strong acid, it completely dissociates into H+ and Br- ions. Therefore, this solution does not contain a significant concentration of the weak acid and its conjugate base, so it is not a buffer.

In summary, only the solution of 0.1 M HF + 0.1 M NaF is considered a buffer because it contains a weak acid and its conjugate base at appreciable concentrations.