1. Types of Chemical Reactions & Solution Stoichiometry
Chapter 4

2. Water is the dissolving medium, or solvent.
Aqueous Solutions
Water is the dissolving medium, or solvent.

3. Some Properties of Water
Water is able to dissolve so many substances because:
Water is “bent” or V-shaped.
105° bond angle
The O-H bonds are covalent.
Water is a polar molecule.
Hydration occurs when salts dissolve in water.

4. Water is a polar molecule because it is a bent
molecule. The hydrogen end is + while the oxygen
end is -, Delta () is a partial charge--less than 1.

5. Polar water molecules interact with the positive
and negative ions of a salt, assisting in the
dissolving process. This process is called hydration.

6. A Solute dissolves in water (or other “solvent”)
changes phase (if different from the solvent)
is present in lesser amount (if the same phase as the solvent)

7. A Solvent retains its phase (if different from the solute)
is present in greater amount (if the same phase as the solute)

8. Solubility The general rule for solubility is: “Like dissolves like.”
Polar water molecules can dissolve other polar molecules such as alcohol and, also, ionic substances such as NaCl.
Nonpolar molecules can dissolve other nonpolar molecules but not polar or ionic substances. Gasoline can dissolve grease.

9. Miscibility
Miscible -- two substances that will mix together in any proportion to make a solution. Alcohol and water are miscible because they are both polar and form hydrogen bonds.(compounds that have hydrogen bonding readily dissolve)
Immiscible -- two substances that will not dissolve in each other. Oil and vinegar are immiscible because oil is nonpolar and vinegar is polar.

10. Solubility
How does the rule “Like dissolves like.” apply to cleaning paint brushes used for latex paint as opposed to those used with oil-based paint?
C6H14 H20
I2 C6H14
H20 I2
NaNO3 H20
HF H20

11. Electrolytes & Nonelectrolytes
An electrolyte is a material that dissolves in water to give a solution that conducts an electric current.
A nonelectrolyte is a substance which, when dissolved in water, gives a nonconducting solution.

12. pure H2O, sugar solution, glycerol
Electrolytes
Strong - conduct current efficiently and are soluble salts, strong acids, and strong bases.
NaCl, KNO3, HNO3, NaOH
Weak - conduct only a small current and are weak acids and weak bases.
HC2H3O2, aq. NH3, tap H2O
Non - no current flows and are molecular substances
pure H2O, sugar solution, glycerol

13. Electrical conductivity of aqueous solutions. a) strong
electrolyte b) weak electrolyte c) nonelectrolyte in solution.
Svante Arrhenius first identified these electrical properties.

14. When BaCl2 dissolves, the Ba2+ and Cl- ions are randomly
dispersed in the water. BaCl2 is a strong electrolyte.

15. Acids
Strong acids - dissociate completely (~100 %) to produce H+ in solution
HCl, H2SO4, HNO3, HBr, HI, & HClO4
Weak acids - dissociate to a slight extent (~ 1 %) to give H+ in solution
HC2H3O2, HCOOH, HNO2, & H2SO3

16. HCl is completely ionized and is a strong electrolyte.

17. Bases
Strong bases - react completely with water to give OH ions. sodium hydroxide
NaOH(s) ---> Na+(aq) + OH-(aq)
Weak bases - react only slightly with water to give OH ions. ammonia
NH3(aq) + HOH(l) <---> NH4+(aq) + OH-(aq)

18. An aqueous solution of sodium hydroxide which is
a strong bases dissociating almost 100 %.

19. Acetic acid(CH3COOH) exists in water mostly as undissociated
molecules. Only a small percent of the molecules are ionized.

20. Write the equation of the dissolving of the following compounds.
CaCl2
HCl
Fe(NO3)3
KBr
(NH4)2Cr2O7

21. Molarity (M) = moles of solute per volume of solution in liters:
1. Calculate the molarity of a solution prepared by dissolving 11.5 g of solid NaOH in enough water to make 1.50 L of solution.
2. Calculate the molarity of a solution prepared by dissolving 1.56 g of gaseous HCl in enough water to make mL of solution.

23. Calculating moles in a solution
How many moles of Co(NO3)2 are present in mL of a 0.75 M Co(NO3)2 solution?
How many moles of nitrate ions are present in mL of a 0.75 M Co(NO3)2 solution?

25. Calculating moles in a solution
Calculate the moles of each of the ions in ml of .20 M Na2CO3solution.
Calculate the moles of potassium ions in ml of the following solution. 2 M K3P

27. Standard Solution
A standard solution is a solution whose concentration is accurately known.
Standard solutions are made using a volumetric flask as follows:
mass the solute accurately and add it to the volumetric flask
add a small quantity of distilled HOH
dissolve the solute by gently swirling the flask
add more distilled HOH until the level of the solution reaches the mark on the neck
invert the capped volumetric 25X to thoroughly mix the solution.

28. Steps involved in making a standard solution.

29. Steps to dilute a stock solution.

30. Common Terms of Solution Concentration
Stock - routinely used solutions prepared in concentrated form.
Concentrated - relatively large ratio of solute to solvent. (5.0 M NaCl)
Dilute - relatively small ratio of solute to solvent. (0.01 M NaCl)

33. When diluting stock solutions, the moles of solute after dilution must equal the moles of solute before dilution. Stock solutions are diluted using either a measuring or a delivery pipet and a volumetric flask.
What volume of 6 M sulfuric acid must be used to prepare 600ml of a 1.0 M H2SO4 solution?
use dilution formula
What volume of 2 M sulfuric acid must be used to prepare 1 L of a .5 M H2SO4 solution?

35. Types of Solution Reactions
Precipitation reactions
AgNO3(aq) + NaCl(aq)  AgCl(s) + NaNO3(aq)
Acid-base reactions
NaOH(aq) + HCl(aq)  NaCl(aq) + H2O(l)
Oxidation-reduction reactions
Fe2O3(s) + 2Al(s)  2Fe(l) + Al2O3(s)

36. 1.      Which of the following substances would you expect to be insoluble in water?
Barium hydroxide Hydrochloric acid
Magnesium sulfate Ammonium nitrate
Silver chloride Lithium carbonate
Calcium carbonate Barium sulfate
Ammonium acetate Lead I Chloride
Sodium hydroxide Ammonium nitrate
Silver nitrate

37. Solubility
Using the solubility rules, predict what will happen when the following pairs of solutions are mixed.
a) KOH(aq) & Mg(NO3)2(aq)
b) Na2SO4(aq) & Pb(NO3)2(aq)
c) KNO3(aq) & BaCl2(aq)
Mg(OH)2(s) forms
PbSO4(s) forms
No precipitate forms

38. Describing Reactions in Solution
1. Molecular equation (reactants and products as compounds)
AgNO3(aq) + NaCl(aq)  AgCl(s) + NaNO3(aq)
2. Complete ionic equation (all strong electrolytes shown as ions)
Ag+(aq) + NO3(aq) + Na+(aq) + Cl(aq) 
AgCl(s) + Na+(aq) + NO3(aq)

39. Describing Reactions in Solution (continued)
3. Net ionic equation (show only components that actually react)
Ag+(aq) + Cl(aq)  AgCl(s)
Na+ and NO3 are spectator ions.

40. Write the balanced complete ionic and net ionic equations:
CuSO4(aq) + LiCl(aq) →
P108 q 28

41. Sodium Sulfate and Lead II Nitrate

43. Old limiting problem to compare
If 68.5 g of CO(g) is reacted with 8.60 g of H2(g), what is the theoretical yield of methanol that can be produced? __H2(g) + __CO(g) ---> __CH3OH(l)

44. Precipitation Calculations
When aqueous solutions of Na2SO4 & Pb(NO3)2 are mixed. Calculate the mass of the percipitate formed when 1.25 L of M Pb(NO3)2 & 2.00 L of M Na2SO4 are mixed. 1.

45. Now it’s the same as limiting you already know.

46. Precipitation Calculations Continued
1 (1.25L)(0.0500mol Pb(NO3)2/1L) =
molPb(NO3)2
(2.00L)(0.0250mol Na2SO4/1L) = molNa2SO4
(Now that you have moles it’s the same as limiting you know .)
2. Divide by the coefficients
Na2SO4 is the limiting reactant
Start with the limititng
3. (0.0500mol Na2SO4)(1mol PbSO4/1mol Na2SO4)
(303.3g/1mol PbSO4) = 15.2 g PbSO4

47. PRACTICE
What mass of precipitate should result when L of M aluminum nitrate solution is mixed with L of 1.50 M sodium hydroxide solution?

49. What is the net ionic equation?
What mass of precipitate should result when L of M aluminum nitrate solution is mixed with L of .50 M sodium hydroxide solution?
What is the net ionic equation? P

51. Mixed Limiting
A .750 g sample of Iron II Chloride is dissolved in water and a mixed with
22.40 ml of .515M AgNO3.
Calculate the grams of precipitate.

53. Practice precipitation
What mass of Fe(OH)3 is produced when 35.ml of a .250M Fe(NO3)3 solution is mixed with 55 ml of a M KOH?
Green book p 95

55. In the experiment, a student is given 2
In the experiment, a student is given 2.94 g of a mixture containing anhydrous MgCl2 and KNO3 . To determine the percentage by mass of MgCl2 in the mixture, the student uses excess AgNO3(aq) to precipitate the chloride ion as AgCl(s). The student determines the mass of the AgCl precipitate to be 5.48 g. On the basis of this information, calculate The number of moles of MgCl2 in the original mixture.

59. Green book review p106 # 44
practice gravimetric analysis A 2.10g sample of silver alloy was dissolved and the precipitated as AgBr. After washing and drying the silver bromide weighed 2.00g. Calculate the percentage silver in the alloy.

64. What volume of M silver nitrate will be required to precipitate as silver bromide all the bromide ion in 35.0 mL of M calcium bromide?