1.12 Acids and bases

• What is a Brønsted-Lowry acid?

  proton (H+) donor
• What do Brønsted-Lowry acids form when reacted with water?

  H3O+ (hydronium ions)
• What is a Brønsted-Lowry base?

  proton (H+) acceptor
• What do Brønsted-Lowry bases form when reacted with water?

  OH- hydroxide ions
• What is a strong acid/base?

  An acid/base that is completely ionised in aqueous solution, dissociating fully into its ions.
• What is a weak acid/base?

  An acid/base that partly ionises in aqueous solutions, only partially dissociating into its ions.
• Give an example of some strong acids.

  HCl, H2SO4, HNO3
• Give an example of a weak acid.

  Any organic acid e.g. Ethanoic CH3COOH
• Give an example of some strong bases

  NaOH, KOH
• Give an example of a weak base

  NH3
• How many mols of H+ is realised per mol of monoprotic acid?

  One
• How many mols of H+ are released per mol of diprotic acid?

  Two
• How do you calculate pH from conc of H+

  pH = -log(H+)
• How do you calculate H+ conc from pH?

  H+ = 10^-pH
• How do you calculate new H+ when a solution has been mixed with another?

  New H+ = conc of old solution X (old volume/new volume)
• How do you calculate Kc?

  H+ X OH- / H2O
• How do you calculate Kw?

  Kw = H+ X OH-
• What is Kw at room temp (25 degrees)

  10^-14
• How do you calculate H+ from Kw?

  H+ = square root of Kw
• How do you calculate Ka?

  Ka = H+ X A- / HA
• How do you calculate PKa ?

  -logKa
• How do you calculate Ka from PKa?

  Ka = 10^-pKa
• How do you calculate the pH of a solution after neutralisation reaction?

  Find moles

  Find excess moles from ice table

  Convert to conc

  Find pH
• If Ka is high is the acid strong or weak?

  Strong
• If the PKa is high is the acid strong or weak?

  Weak
• Metal + acid =?

  Metal + acid = salt + hydrogen
• Acid + base =?

  Acid + base = salt + water
• Acid + carbonate = ?

  Acid + carbonate = salt + water + carbon dioxide
• Where on a titration curve is the naturalisation point?

  Middle of the vertical line.
• Where on a titration curve is the half neutralisation point?


  Half way between 0 and equivalence point.
• What can the half neutralisation point let us work out?

  At this point HA conc = A- conc

  
  

  So Ka = H+ conc

  
  

  So -log Ka = -logH+ and therefore PKa = pH
• Why are diprotic titration curves different?

  Protons are released at 2 different points so there are two equivalence points.
• Which two indicators are used in titrations?

  Methyl orange and phenophalein
• What pH does methyl orange change colour?

  3-4.5
• What pH does phenophalein change colour at?

  8-10
• What indicator do we use for strong acid + strong base?

  Methyl orange
• What indicator do we use for strong acid + weak base?

  Methyl orange
• What indicator do we use for weak acid + strong base?

  Phenophalein
• What indicator do we use for weak acid + weak base?

  None - a pH meter is used as there is no sharp pH change.
• Where is the half neutralisation point on a titration pH curve?

  Halfway between 0 and the neutralisation point.