1. Acids Lesson 17 Buffers Indicators

4. Buffer Solutions Buffer solutions are equilibrium systems, which maintain a relatively constant pH when small amounts of acids or bases are added. Acid Buffer Recipe Weak Acid + Salt (conjugate) HF NaF Buffer EquationSame as weak acid HF ⇋ H + +F -

5. [High][low][High] [HF] is high and [H + ] is low because HF is a weak acid. [F - ] is high due to adding the salt NaF. This buffer solution can shift left or right and the [H + ] and the pH remains fairly constant.

6. Base Buffer Recipe Weak Base + Salt (conjugate) NH 3 NH 4 Cl Buffer EquationSame as weak base NH 3 +H 2 O ⇋ NH 4 + +OH - [High][High][Low]

7. Fill in the blanks to get buffer solutions. AcidBase HCNNaCN H 2 CO 3 NaHCO 3 H 3 PO 4 NaH 2 PO 4 CH 3 COOHKCH 3 COO NH 4 ClNH 3 NaHCO 3 Na 2 CO 3 NaH 2 PO 4 Na 2 HPO 4

8. Buffer Animation Buffer Animation 1

9. Buffer Application 1.Pick the two buffer solutions A.NH 4 Cland HCl B.NaClandNaOH C.HCNandNaCN D.NH 4 ClandNH 3  

10. 2.Write the equations for the above two buffer solutions. Label the concentrations as high or low. HCN ⇋ H + +CN - [High] [Low] [High] NH 3 +H 2 O=NH 4 + +OH - [High] [High] [Low]

11. 3.A few drops of 0.10 M NaOH is added to a buffer solution at pH = 5.00. The new pH could be: A4.98 B.5.02 C.8.05 D.2.11 

12. AcidBase YellowRed ShiftColour At pH < 10.1LeftYellow[HInd] > [Ind - ] At pH > 12.0RightRed[HInd] < [Ind - ] At pH = 11.05MiddleOrange[HInd] = [Ind - ] HInd ⇋ H + +Ind - Alizarin Yellow Indicators

13. @ the transition point [HInd] = [Ind - ] Ka = [H + ] Ka = 10 -pH Ka = 10 -11.05 = 9 x 10 -12