Consinder the buffer system of nitrous acid HNO2 and its salt NaNO2?

Question

HNO2(aq)+H2O(l)=H3O+(AQ)+NO2-(AQ)
A. What is the purpose of a buffer system?
B. What is the purpose of NaNO2 in the buffer?
C. How does the bugger react when some H3O+ is added?
D. How does the buffer react when sokme OH- is added?

Answer 1

Buffer solutions are used to maintain a pH in a narrow range if there are additions of acids or bases to the solution.

The sodium nitrite adds nitrite ion to the solution. In most acid buffers, the cation (nitrite) conc is about equal to that of the weak acid. In such a set-up, [H+] appx equals Ka. If some more acid (H3O+) is added, it reacts with the nitrite ion to form more undissociated acid. There is a change in [H]+, but it is much less than would happen if there were no buffer. If some more base [OH-] is added, the undissociated acid reacts with it to form additional nitrite ion. Again, there is a change in [H+], but not as much as would happen if there were no buffer.

BTW: The buffer "works" as long as the conc. of the cation and weak acid is greater than the conc. of acid or base added. The buffer action can be exhausted if the added conc. becomes too great, because there is no longer enough cation or weak acid to react with the incoming acid or base.

Answer 2

The purpose of NaNo2 in the buffer is that the salt in a buffer is needed to neutralize any acid added.