Unit Twelve Acids and Bases

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Unit TwelveAcids and Bases
2
Neutralizations

• Are reactions in which an acid and a base react
  in an aqueous solution to produce a salt and
  water
• General Equation
• HX(aq) MOH(aq) ? MX(aq) H2O(l) (or
  HOH)
• Complete Ionic Equation
• H(aq) X-(aq) M(aq) OH-(aq) ?
  M(aq) X-(aq) H2O(l)
• Net Ionic Equation H(aq) OH-(aq) ?
  H2O(l)

3
Neutralization Practice

• HCl(aq) NaOH(aq) ?
• _____________________? K2SO4 (aq) ________
• HNO3(aq) Mg(OH)2(aq) ?

H2O(l) NaCl(aq)
H2SO4(aq) 2KOH(aq)
H2O(l)
2
2H2O(l) Mg(NO3)2(aq)
2
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Titration - An experimental technique for
determining the concentration of an unknown
acid/base by comparing it to an acid/base
solution of known concentration

• How is this done?
• By gradually adding and carefully measuring the
  amount of acid added to a measured amount of base
  (or vice versa) until the endpoint is reached
• What is an endpoint?
• The point in the titration when the number of
  moles of OH- added equals the number of moles of
  H originally in solution
• How do we know when the endpoint is reached?
• The endpoint is usually signaled by an indicator

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Indicators

• A dye whose color depends on the pH of the
  solution
• There are many different indicators to indicate
  different ranges of pH
• Phenolphthalein turns from clear (when acidic) to
  pink (when basic)

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Practice Problems

• 100.0 mL of an unknown acid is neutralized by
  75.0 mL of 3.0 M NaOH. What is the concentration
  of the unknown acid?
• During a titration experiment, 0.250 L of 0.200 M
  NaOH was needed to completely neutralize 1.00 L
  of an HCl solution. What was the molarity of the
  original HCl solution?
• In another titration experiment, 30.0 mL of 0.150
  M KOH is needed to neutralize 50.0 mL of a fresh
  HNO3 solution. What was the concentration of the
  nitric acid?

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10 - 14
6 7.6
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• Worksheet Three is due Friday
• Tomorrow there will be an opportunity to retake
  the Unit Eleven test if you choose. You need to
  let me know by the end of the day (3-14)