Solutions

1
Solutions

• Solute what is dissolved
• Solvent what the solute is dissolved into.
• Aqueous solutions have water as the solvent.

2
Water solubility depends on

• Polarity of solute and solvent.
• Relative attractions of the ions for each other
  as opposed to the ions attraction for the water
  molecules

3
Strong electrolytes

• A solution of a strong electrolyte is able to
  conduct a current efficiently
• The ionic substance completely ionizes. Soluble
  salts, strong acids, strong bases

4
Weak Electrolytes

• Solutions that do not conduct electricity
  efficiently.
• Only a small amount of the ionic compound ionizes
  Insoluble or slightly soluble salts, weak acids
  or bases

5
Nonelectrolytes

• Solutions that do not conduct electricity.
• Solute is polar but not ionic so no ions can be
  produced.
• Molecular compounds in solution.

6
Molarity (M)

• M moles of solute
• liters of solution

7

• A solution of ethanol is prepared by dissolving
  75.0 mL of ethanol (density 0.79g/mL) in enough
  water to make 250.0 mL of solution. What is the
  molarity of this solution?

8

• Calculate the concentration of all ions present
  in a solution made from 1.00g of K2SO4 in 250.0
  mL of solution.

9

• How would you prepare 500 mL of a 0.500M solution
  of sodium carbonate from the pure solid?

10
Dilutions

• Adding water to a stock or concentrated solution
  in order to prepare a lower molarity solution.
• Moles of solute before dilution moles of solute
  after dilution

11
Mmolarity Vvolume

• M1xV1 moles of solute before dilution
• M2xV2 moles of solute after dilution
• M1xV1 M2xV2

12

• How would you prepare 250 mL of 6.0M sulfuric
  acid from concentrated (18M) sulfuric acid?

13
Precipitation Reactions

• When two solutions are mixed an insoluble product
  is formed.
• To predict the product of these reactions
  solubility rules must be known.
• Table 4.1 p. 152

14
Write the balanced molecular, the complete ionic,
and the net ionic equations for the following

• FeSO4(aq) KCl(aq)
• Al(NO3)3(aq) Ba(OH)2(aq)
• CaCl2(aq) Na2SO4(aq)
• K2S(aq) Ni(NO3)2(aq

15
Solution Stoichiometry

• Identify reactants and products
• Balance net ionic equation
• Calculate moles of reactants
• Determine limiting reactant
• Calculate moles of product
• Convert to grams or other unit

16

• What volume of 0.100M Na3PO4 is required to
  precipitate all the lead(II) ions from 150.0 mL
  of 0.250M Pb(NO3)2 ?

17

• What mass of barium sulfate can be produced when
  100.0 mL of a 0.100M solution of barium chloride
  is mixed with 100.0 mL of a 0.100M solution of
  iron(III) sulfate?

18
Acid Base Reactions

• Acid- proton donor
• Base proton acceptor
• Acid base? salt water
• Neutralization reaction.

19
Write the balanced molecular, the complete ionic,
and the net ionic equations for the following

• HNO3(aq) Al(OH)3
• HC2H3O2(aq) KOH(aq)
• Ca(OH)2(aq) HCl(aq)

20

• Hydrochloric acid (75.0 mL of 0.250M) is added to
  225.0 mLof 0.0550M Ba(OH)2 solution. What is the
  concentration of the excess H or OH- ions left
  in solution?

21
Oxidation-Reduction Reactions

• Reactions where one or more electrons are
  transferred.
• The oxidation state or number of an element will
  change during the reaction.
• Rules for assigning oxidation numbers Table 4.2
  p.167

22

• Species Oxidized - increase in oxidation state ,
  lose electron(s) and act as the reducing agent.
• Species Reduced - decrease in oxidation state,
  gain electron(s) and act as the oxidizing agent.

23
Assign oxidation states to all atoms

• UO22
• As2O3
• NaBiO3
• Cl2
• Mg2P2O7

24
Specify which of the following are redox
reactions, identify the oxidizing agent, the
reducing agent, the species being oxidized and
the species being reduced

• Cu(s) 2Ag(aq) ? 2Ag(s) Cu2(aq)
• HCl(g) NH3(g) ? NH4Cl(s)
• SiCl4(l) 2Mg(s)? 2MgCl2(s) Si(s)

25
Balancing Redox Equations

• Write separate half reactions
• Balance each half reaction
• Elements except H and O
• Oxygen using water
• Hydrogen using H
• Charge using electrons

26
Balancing Redox Equations

• Equalize electrons transferred by multiplying
  half reactions by whole numbers.
• Add half reactions together
• If the reaction is in a basic environment
  neutralize the H ions with OH- ions.

27
Balance the following in acid solution

• Cr2O7(aq) Cl-(aq)? Cr3(aq) Cl2(g)
• Pb(s)PbO2(s)H2SO4(aq)?PbSO4(s)
• Mn2(aq)NaBiO3(s)?Bi3(aq)MnO4(aq)

28
Balance the following in basic solution

• Cr(s)CrO42-(aq)? Cr(OH)3(s)
• MNO4-(aq) S2-(aq)? MnS(s) S(s)
• CN-(aq)MnO4-(aq)?CN-(aq)MnO2(s)