Which of the following has the strongest buffering capacity? a. h2o b. 0.1 m hcl c. 0.1 m carbonic/bicarbonate (h2co3/hco3-) at ph ~pka d. 0.2 m carbonic/bicarbonate (h2co3/hco3-) at ph ~pka

Explanation:

(A)   As we know that carbonic acid () and Sodium bicarbonate () forms an acidic buffer.

Therefore, pH of an acidic buffer is given by Hendeerson-Hasselbalch equation as follows.

               pH = ........... (1)

So mathematically,  if [Salt] = [Acid]  then = 1 .

And,   = 0

Therefore, equation (1) gives us the following.

         pH = (when acid and salt are equal in concentration)

Hence, of (carbonic acid) is 6.35.

And, with this we have following results.

In (A) and (D) we have the case \frac{[NaHCO_{3}]}{[H_{2}CO_{3}]}[/tex] i.e. [Salt] = [Acid].

Hence, for the cases pH = = 6.35.

(B)     = 0.045 M and,   = 0.45 M

Hence,   pH =

                     =

                     = 6.35 + (-1)

                     = 5.35

Therefore, it means that this buffer will be most suitable buffer as it has pH on acidic side and addition of slight excess base will not affect much of its pH value.

(C)     = 0.45 M

                          = 0.045 M

So,       pH =

                  =

                  = 6.35 + (+1)

                 = 7.35

This means that pH on Basic side makes it no more acidic buffer.

chemical changes occur when a substance combines with another to form a new substance, called chemical synthesis or, alternatively, chemical decomposition into two or more different substances. these processes are called chemical reactions and, in general, are not reversible except by further chemical reactions. some reactions produce heat and are called exothermic reactions and others may require heat to enable the reaction to occur, which are called endothermic reactions. understanding chemical changes is a major part of the science of chemistry.