Solution Chemistry (Chp. 7)

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Solution Chemistry (Chp. 7)

• Chemistry 2202

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Topics

• Molar Concentration (mol/L)
• Dilutions
• Concentration (pp. 255 263)
• Solution Process
• Solution Preparation
• Solution Stoichiometry
• Dissociation

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Terms

• solution
• solvent
• solute
• concentrated
• dilute
• aqueous
• miscible
• Immiscible
• alloy
• solubility

• molar solubility
• saturated
• unsaturated
• supersaturated
• dissociation
• electrolyte
• non-electrolyte
• filtrate
• precipitate

limiting reagent excess reagent actual
yield theoretical yield decanting pipetting dynam
ic equilibrium
x
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• Define the terms in bold and italics from pp. 237
  240.
• Solids, liquids, and gases can combine to produce
  9 different types of solution. Give an example
  of each type.
• p. 242 s 5, 7, 9, 10

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Terms

• alloy
• solubility
• molar solubility
• saturated
• unsaturated
• supersaturated
• dynamic equilibrium

• solution
• solvent
• solute
• concentrated
• dilute
• aqueous
• miscible
• immiscible

x
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Factors Affecting Solubility (pp.243 254)

• List 3 factors that affect the rate of
  dissolving.
• How does each of the following affect solubility?
• particle size
• temperature
• pressure

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Factors Affecting Solubility

• What type of solvent will dissolve
• polar solutes
• nonpolar solutes
• ionic solutes
• Why do some ionic compounds have low solubility
  in water?
• p. 254 s 1, 2, 4 - 6

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Section 7.2 (pp. 243 252)

• State the generalizations regarding solubility
  and solutions (in italics)
• Define terms (in bold)

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• rate of dissolving dipole
• ion-dipole attractions
• hydrated
• electrolyte.
• non-electrolytes

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Rate of Dissolving

• for most solids, the rate of dissolving is
  greater at higher temperatures
• stirring a mixture or by shaking the container
  increases the rate of dissolving.
• decreasing the size of the particles increases
  the rate of dissolving.

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Like Dissolves Like

• ionic solutes and polar covalent solutes both
  dissolve in polar solvents
• non-polar solutes dissolve in non-polar solvents.
  

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Solubility

• small molecules are often more soluble than
  larger molecules.
• the solubility of most solids increases with
  temperature.
• the solubility of most liquids is not greatly
  affected by temperature.
• the solubility of gases decreases as temperature
  increases

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Solubility

• An increase in pressure increases the solubility
  of a gas in a liquid.

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Applications

• 1. An opened soft drink goes flat faster if not
  refrigerated.
• 2. Warming of pond water may not be healthy for
  the fish living in it.
• 3. After pouring 5 glasses of pop from a 2 litre
  container, Jonny stoppered the bottle and crushed
  it to prevent the remaining pop from going flat.

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Molar Concentration

• Review
• - Find the molar mass of Ca(OH)2
• - How many moles in 45.67 g of Ca(OH)2?
• - Find the mass of 0.987 mol of Ca(OH)2.

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Molar Concentration

• The terms concentrated and dilute are qualitative
  descriptions of solubility.
• A quantitative measure of solubility uses
  numbers to describe the concentration of a
  solution.

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Molar Concentration

• The MOLAR CONCENTRATION of a solution is the
  number of moles of solute (n) per litre of
  solution (v).

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Molar Concentration

• FORMULA
• Molar Concentration number of moles
• volume in litres
• C n
• V

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• eg. Calculate the molar concentration of
• 4.65 mol of NaOH is dissolved to prepare 2.83 L
  of solution.
• 15.50 g of NaOH is dissolved to prepare 475 mL
  of solution.
• p. 268 - 19

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• Eg. Calculate the following
• the number of moles in 4.68 L of 0.100 mol/L KCl
  solution.
• the mass of KCl in 268 mL of 2.50 mol/L KCl
  solution.

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• the volume of 6.00 mol/L HCl(aq) that can be made
  using 0.500 mol of HCl.
• the volume of 1.60 mol/L HCl(aq) that can be made
  using 20.0 g of HCl.
• p. 268 s20-24

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Dilution (p. 272)
Number of moles before dilution

• When a solution is diluted
• The concentration decreases
• The volume increases
• The number of moles remains the same
• ni nf

Number of moles after dilution
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Dilution (p. 272)

• ni nf
• Ci Vi Cf Vf
• eg. Calculate the molar concentration of a
  vinegar solution prepared by diluting 10.0 mL of
  a 17.4 mol/L solution to a final volume of 3.50 L.

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• p. 273 s 25 27
• p. 276 s 1, 2, 4, 5
• DONT SHOW UP UNLESS
• THIS IS DONE!!

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Solution Preparation Dilution

• standard solution a solution of known
  concentration
• volumetric flask a flat-bottomed glass vessel
  that is used to prepare a standard solution
• delivery pipet pipets that accurately measure
  one volume
• graduated pipet pipets that have a series of
  lines that can be use to measure many different
  volumes

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To prepare a standard solution

• 1. calculate the mass of solute needed
• 2. weigh out the desired mass
• 3. dissolve the solute in a beaker using less
  than the desired volume
• 4. transfer the solution to a volumetric flask
  (rinse the beaker into the flask)
• 5. add water until the bottom of the meniscus is
  at the etched line

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To dilute a standard solution

• 1. Rinse the pipet several times with deionized
  water.
• 2. Rinse the pipet twice with the standard
  solution.
• 3. Use the pipet to transfer the required volume.
• 4. Add enough water to bring the solution to its
  final volume.

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Percent Concentration

• Concentration may also be given as a .
• The amount of solute is a percentage of the total
  volume/mass of solution.
• liquids in liquids - v/v
• solids in liquids - m/v
• solids in solids - m/m

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Percent Concentration
p. 258 s 1 3 DSUUTID!!
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• p. 261 s 5 9
• DSUUTID!!

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• p. 263 s 10 13
• DSUUTID!!

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Concentration in ppm and ppb

• Parts per million (ppm) and parts per billion
  (ppb) are used for extremely small concentrations

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• eg. 5.00 mg of NaF is dissolved in 100.0 kg of
  solution. Calculate the concentration in
• a) ppm
• b) ppb

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• ppm 0.005 g x 106
• 100,000 g
• 0.05 ppm
• ppb 0.005 g x 109
• 100,000 g
• 50.0 ppb

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• p. 265 s 15 17
• pp. 277, 278
• s 11, 13, 15 18, 20
• DONT SHOW UP UNLESS
• THIS IS DONE!!

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Solution Stoichiometry

• 1. Write a balanced equation
• 2. Calculate moles given
• nm/M OR nCV
• 3. Mole ratios
• 4. Calculate required quantity

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Solution Stoichiometry

• eg. 45.0 mL of a HCl(aq) solution is used to
  neutralize 30.0 mL of a 2.48 mol/L NaOH solution.
• Calculate the molar concentration of the HCl(aq)
  solution.
• p. 304 s 16, 17, 18
• Worksheet

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Sample Problems

• 1. What mass of copper metal is needed to react
  with 250.0 mL of 0.100 mol/L silver nitrate
  solution?
• 2. Calculate the volume of 2.00 M HCl(aq) needed
  to neutralize 1.20 g of dissolved NaOH.
• 3. What volume of 3.00 mol/L HNO3(aq) is needed
  to neutralize 450.0 mL of 0.100 mol/L Sr(OH)2(aq)?

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Sample Problem Solutions

• Cu(s) 2 AgNO3(aq) ? 2 Ag(s) Cu(NO3)2(aq)
• Step 2 n 0.02500 mol AgNO3
• Step 3 n 0.01250 mol Cu
• Step 4 m 0.794 g Cu

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Sample Problem Solutions

• HCl(aq) NaOH(aq) ? NaCl(aq) H2O(l)
• Step 2 n 0.0300 mol NaOH
• Step 3 n 0.0300 mol HCl
• Step 4 V 0.0150 L HCl

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Sample Problem Solutions

• 2 HNO3(aq) Sr(OH)2(aq) ?
• 2 H2O(l) Sr(NO3)2(aq)
• Step 2 n 0.04500 mol Sr(OH)2
• Step 3 n 0.0900 mol HNO3
• Step 4 V 0.0300 mol/L HNO3

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The Solution Process (p. 299)

• Dissociation occurs when an ionic compound breaks
  into ions as it dissolves in water.
• A dissociation equation shows what happens to an
  ionic compound in water.
• eg. NaCl(s) ? Na(aq) Cl-(aq)
• K2SO4(s) ? 2 K(aq) SO42-(aq)

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The Solution Process (p. 299)

• Solutions of ionic compounds conduct electric
  current.
• A solute that conducts an electric current in an
  aqueous solution is called an electrolyte.

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The Solution Process (p. 299)

• Acids are also electrolytes.
• Acids form ions when dissolved in water.
• eg. H2SO4(aq) ? 2 H(aq) SO42-(aq)
• HCl(s) ? H(aq) Cl-(aq)

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The Solution Process (p. 299)

• Molecular Compounds DO NOT dissociate in water.
• eg. C12H22O11(s) ? C12H22O11(aq)
• Because they DO NOT conduct electric current in
  solution, molecular compounds are
  non-electrolytes.

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The Solution Process (p. 299)

• The molar concentration of any dissolved ion is
  calculated using the ratio from the dissociation
  equation.
• eq. What is the molar concentration of each ion
  in a 5.00 mol/L MgCl2(aq) solution

5.00 mol/L
5.00 mol/L
10.00 mol/L
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• p. 300 s 7 9
• What mass of calcium chloride is required to
  prepare 2.00 L of 0.120 mol/L Cl-(aq) solution?
• p. 302 14
• p. 311 s 11, 12, 16, 18