A 11 mL solution of 0.04 M HCI is titrated with 0.04 M NaOH to give the followin
ID: 546984 • Letter: A
Question
A 11 mL solution of 0.04 M HCI is titrated with 0.04 M NaOH to give the following titration curve. Determine the key features of this curve. (The titration curve is approximate and may not show all aspects adequately.) pH 12 10 8 5.51 165 22 Base Added (mL) The titration curve has the following features (1) Before any base is added, the pH of the starting solution of 0.04 M HCl is (2) When small amounts of base are added, up to about 9 ml, the pHSelect-.gradually but remains in the Select- region. In this area, the solution contains an excess of Hyo ons. (3) At and around the equivalence point, the pH rises dramatically going from the acidic region to the basic region. At the equivalence point, when H30+ - OH- the pHis (4) As more base is added beyond the equivalence point, the pH Select gradually within the region. In this area, the solution contains an excess of OH- ions. SelectExplanation / Answer
1) the pH of the acid at start
pH = -log 0.04
= 1.3979
2) When small amounts of base are added
HCl + NaOH ---------------> NaCl + H2O
11x0.04 9x0.04 0 0 initial mmoles
0.08 0 0.36 - after reaction
Thus [H+] = 0.08/20
pH = -log (0.08/20)
= 2.3979
When small amounts of base are added upto 9 mL, the pH increases gradually, but remains in the acidic region, In this region the solution contains an excess of H3O+ ions.
3) Around the equivalent point the pH rises dramatically, from acidic region to basi c region. At equivalence point, when{H3O+] = [OH-] , th epHof the solution is 7.0 (neutral)
4) As more base is added, beyond the equivalence point, the pH increases gradually within the basic region.
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