Equilibria 2

• What does pH measure in a solution?

  Concentration of [H+] or [H3O+]
• How is pH determined mathematically?

  pH = - log [H3O+]
• What is the formula for [H3O+] for weak acids?

  [H3O+] = KaCa
• What is the formula for [H3O+] for weak bases?

  [H3O+] = $\frac{K_a K_w}{C_b}$
• How do you find Ka from pKa?

  Ka = $10^{-pKa}$
• What are buffers?

  Compounds that resist pH changes
• What typically comprises a buffer?

  A weak acid and its conjugate base
• How do buffers work when H+ is added?

  Equilibrium shifts to form undissociated acid
• How do buffers work when OH- is added?

  Equilibrium shifts to form the salt
• What is the Henderson-Hasselbalch equation?

  pH = pKa + log(Cb/Ca)
• What happens to pH when salt is added to a buffer?

  pH increases significantly
• Why are buffer solutions important?

  They maintain correct pH for enzymes
• What buffer is present in blood plasma?

  Carbonic acid and bicarbonate
• What is the pH range maintained by blood plasma buffers?

  Between 7.35 and 7.45
• How does titration illustrate the effect of buffers?

  It shows pH changes with acid/base addition

  
• What happens at the titration endpoint?

  All acid converts to conjugate base

  
• What occurs at half equivalence point?

  Equal amounts of acid and salt present

  
• What is the pH at half equivalence point?

  pH = pKa

  
• How do you calculate molecular weight from titration data?

  Molecular weight = mass / moles
• What is the formula for calculating number of moles?

  Number of moles = Molarity x Volume
• What is the unit for molarity?

  M (mol/L)
• What is the conversion between liters and milliliters?

  1 L = 1000 mL
• What is the conversion between milliliters and liters?

  1 mL = 1/1000 L