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Acids Lesson 17 Buffers Indicators

Acids Lesson 17 Buffers Indicators. 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 Equation Same as weak acid

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Acids Lesson 17 Buffers Indicators

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  1. Acids Lesson 17 Buffers Indicators

  2. 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-

  3. HF ⇋ H+ + F- [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.

  4. Base Buffer Recipe Weak Base + Salt (conjugate) NH3 NH4Cl Buffer EquationSame as weak base NH3 + H2O ⇋ NH4+ + OH- [High] [High] [Low]

  5. Fill in the blanks to get buffer solutions. Acid Base HCN NaCN H2CO3 NaHCO3 H3PO4 NaH2PO4 CH3COOH KCH3COO NH4Cl NH3 Na2CO3 NaHCO3 Na2HPO4 NaH2PO4

  6. Buffer Animation 1

  7. Buffer Application 1. Pick the two buffer solutions A. NH4Cl and HCl B. NaCl and NaOH C. HCN and NaCN D. NH4Cl and NH3  

  8.  2. Write the equations for the above two buffer solutions. Label the concentrations as high or low. HCN ⇋ H+ + CN- [High] [Low] [High]   NH3 + H2O = NH4+ + OH- [High] [High] [Low]

  9. A few drops of 0.10 M NaOH is added to a buffer solution at pH = 5.00. • The new pH could be: • A 4.98 • B. 5.02 • C. 8.05 • D. 2.11 

  10. Indicators Alizarin Yellow HInd ⇋ H+ + Ind- Acid Base Yellow Red Shift Colour At pH < 10.1 Left Yellow [HInd] > [Ind-] At pH > 12.0 Right Red [HInd] < [Ind-] At pH = 11.05 Middle Orange [HInd] = [Ind-]

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

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