1. Neutralization

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• 1. Neutralization
• 2. NaOH HCl ? H2O NaCl
• 2NaOH H2SO4 ? 2H2O Na2SO4
• 3. Twice as much HCl was required. Because it
  takes twice as much HCl (one H) as H2SO4 (two Hs)
  to neutralize the same amount of NaOH

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4. H2SO4(aq) 2NaOH(aq) ? 2H2O Na2SO4(aq)
L H2SO4
0.010 L NaOH
0.01714 L 17.1 mL

• 5. H x MA x VA OH x MB x VB

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Titration problems

1. What volume of 0.10 mol/L NaOH is needed to
   neutralize 25.0 mL of 0.15 mol/L H3PO4?
2. 25.0 mL of HCl(aq) was neutralized by 40.0 mL of
   0.10 mol/L Ca(OH)2 solution. What was the
   concentration of HCl?
3. A truck carrying sulfuric acid is in an accident.
   A laboratory analyzes a sample of the spilled
   acid and finds that 20 mL of acid is neutral-ized
   by 60 mL of 4.0 mol/L NaOH solution. What is the
   concentration of the acid?
4. What volume of 1.50 mol/L H2S will neutral-ize a
   solution containing 32.0 g NaOH?

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Titration problems

• 1. (3)(0.15 M)(0.0250 L) (1)(0.10 M)(VB)
• VB (3)(0.15 M)(0.0250 L) / (1)(0.10 M) 0.11 L
• 2. (1)(MA)(0.0250 L) (2)(0.10 M)(0.040 L)
• MA (2)(0.10 M)(0.040 L) / (1)(0.0250 L) 0.32 M
• 3. Sulfuric acid H2SO4
• (2)(MA)(0.020 L) (1)(4.0 mol/L)(0.060 L)
• MA (1)(4.0 M)(0.060 L) / (2)(0.020 L) 6.0 M
  
• 4. mol NaOH 32.0 g x 1 mol/40.00 g 0.800
  (2)(1.50 mol/L)(VA) (1)(0.800 mol)
• VA (1)(0.800 mol) / (2)(1.50 mol/L) 0.267 L

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Titration summary

• For titrations we use the formula
• H x MA x VA OH x MB x VB
• Or NA x VA NB x VB
• NA is the combination of MA and H
• N is also known as normality
• You can think of it a neutralizing power
• We will stick with the first equation, you do not
  have to know N or what it stands for
• This is a simplification of stoichiometry. We
  could get the same answer by working with moles
  (n MV) and by using the balanced chemical
  equation

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Titration showdown

• Titration competition (best with a burette) find
  the concentration of an H2SO4 solution it could
  be anywhere from 0-18 mol/L

• You will use the NaOH that you prepared two weeks
  ago and your vast knowledge of titration
  procedures and formulas.
• The wining team, is the team closest to the
  correct value.
• The only restriction is dont put base in the
  burette only acid.

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Sources of error

• NaOH was not exactly 0.10 mol/L
• Calculation errors (e.g. converting mL to L)
• Not rinsing and drying the beaker for the acid
• Over titrating (ideally, 2 titrations should be
  done one to get a rough estimate, and one to
  get the exact value).
• Acid or base left on the side of the flask or on
  the tip of the burette (for greater precision,
  water is used to rinse the tip of the burette).
• Errors reading volumes.
• Using pipette (10 mL is measured from 0 mL to 10
  mL, not from 10 mL to empty)
• Using 10 mL of base vs. 25-50 mL

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