Abuffer consists of 0.120 m hno2 and 0.150 m nano2 at 25°c. pka of hno2 is 3.40. a. what is the ph of the buffer? b. what is the ph after the addition of 1.00 ml of 11.6 m hcl to 1.00 l of the buffer solution?

Explanation:

It is known that of = .

(a)  Relation between and is as follows.

Putting the values into the above formula as follows.

                                    =

                                     = 3.347

Also, relation between pH and   is as follows.

              pH =

                     =

                    = 3.44

Therefore, pH of the buffer is 3.44.

(b)   No. of moles of HCl added =

                                            =

                                             = 0.0116 mol

In the given reaction, will react with to form

Hence, before the reaction:

No. of moles of =

                                           = 0.15 mol

And, no. of moles of =

                                               = 0.12 mol

On the other hand, after the reaction :  

No. of moles of = moles present initially - moles added

                                          = (0.15 - 0.0116) mol

                                          = 0.1384 mol

Moles of = moles present initially + moles added

                               = (0.12 + 0.0116) mol

                                = 0.1316 mol

As, =

                         =

                         = 3.347

Since, volume is both in numerator and denominator, we can use mol instead of concentration.

As, pH =

            = 3.347+ log {0.1384/0.1316}

            = 3.369

            = 3.37 (approx)

Thus, we can conclude that pH after the addition of 1.00 mL of 11.6 M HCl to 1.00 L of the buffer solution is 3.37.

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