Solutions

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Chapter 13

• Solutions

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Homework, Chapter 13

• Problems, Pages 460 to 467
• 4, 15, 17, 27, 29, 61, 63, 65, 67, 69
• Blackboard Quiz

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I. Introduction - Definitions

• Solution Homogeneous mixture of two or more
  substances.
• Solvent Single component of a solution which is
  present in greatest amount.
• Solutes Components of a solution which are
  present in smaller amounts.
• Concentration Measure of amount of solute in a
  given volume of solution.
• Solubility The amount of a compound that will
  dissolve in a given volume of solvent.

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II. Concentration Units

• 1. W/V g solute / mL solution x 100
  
• Example 18 g of NaCl is in 200. mL of solution.
  What is NaCl?
• 18 g / 200. mL x 100 9.0
• 2. Parts per Billion (ppb) ng solute / g
  solution (mL if aqueous)
• Example 520 ng of benzene are found in 1.0 L of
  water. What is the ppb?
• ppb 520 ng benzene / 1000 mL 0.52 ng/mL

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II. Concentration Units

• 3. Molarity moles solute / L solution M
  m/L
• - This is the most popular concentration unit.
• - May have to calculate M, L or moles (m). Use
  the equations
• M m/L m MxL L m/M

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II. Concentration Units

• a) What is the M if dissolve 4 moles in 0.5 L?
• M m/L 4 m / 0.5 L 8 m/L or 8 M
• b) 0.80 g of NaOH is dissolved in 200. mL (0.200
  L). Calculate the M
• 0.80 g NaOH x 1 mol NaOH / 40. g NaOH 0.020
  mol NaOH
• M m/L 0.020 mol / 0.200 L 0.10 m/L
  or 0.10 M NaOH
• c) How many moles of HI are in 3.0 L of 2.0 M HI?
• M m/L m M x L 2.0 m/L HI x
  3.0 L 6.0 moles HI

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II. Concentration Units

• D) 40. mL of 0.10 M (m/L) H2SO4 are required to
  react with 30. mL of a solution containing NaOH.
  How many moles of NaOH are present?
• 1 H2SO4 2 NaOH ----------) 1
  Na2SO4 2 H2O
• First calculate moles of H2SO4 and then using the
  balanced equation, calculate moles of NaOH.
• 0.10 m/L H2SO4 x 0.040 L H2SO4 4.0 x 10-3 m
  H2SO4
• 4.0 x 10-3 m H2SO4 x (2 m NaOH / 1 m H2SO4)
  8.0 x 10-3 m NaOH

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II. Concentration Units

• Lab Example 1MnO4- 8H 5Fe2 ---) 1Mn2
  5Fe3 4H2O
• How many mg of Fe2 are in a tablet that required
  9.65 mL of 5.00x10-3 M KMnO4 for titration?
• Moles MnO4- 5.00x10-3 m/L KMnO4 x 9.65
  x10-3 L 4.83x10-5 moles
• Moles of Fe2 4.83x10-5 m MnO4- x 5m Fe2/1m
  MnO4- 2.41x10-4 moles
• mg Fe2 (2.41x10-4 moles Fe2) x (55.9x103 mg
  Fe2/1m Fe2) 13.5 mg Fe2

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Fe Titration Lab
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III. Solubility

• Soluble and Insoluble refer to how much solute
  dissolves in a given solvent with water being the
  most common solvent.
• Group IA, nitrate, acetate and ammonium compounds
  are very soluble in water as an example.
• Water dissolves a large variety of ionic and less
  polar compds.
• Non-polar compounds like organic compounds do not
  dissolve in water, but dissolve in organic
  solvents like hexane or benzene
• The general rule on solubility is Like Dissolves
  Like.
• Questions Why does water generally wash off pop
  stains?
• Why does water not take off grease stains?
• Why does soapy water take off both?