November 10, 2010 Wednesday

Today we started out the class by reviewing for the chemistry test on Friday. Mr. H gave the class ways to review for the test. He told us about a review worksheet on the gbschemphys website. After this we turned to page 13 in our Unit 4 packets and reviewed what we had done the day before.

We know that when an ionic compound dissolves in water, it dissociates into ions. These are the balanced chemical equations which show the dissociation of ionic compounds in water.

a. sodium chloride

NaCl(s) ---> Na+(aq) + Cl-(aq)

b. aluminum nitrate

Al(NO3)3 (s) -----> Al3+(aq) +3 NO3-(aq)

c. barium chloride

BaCl2 ----> Ba2-(aq) +2 Cl-(aq)

d. sodium sulfate

NaSo4(s) ----> 2 Na+(aq) + So4 2-(aq)

We also know from our lab that that Na and NO3 are soluble, but there are more things that are soluble in water. On page 13 of the packet there is a table of solubility rules. The rules for compounds that have high solubility are...

High Solubility

1.All alkali metal and ammonium compounds

2. Hydrogen compounds containing H+

3. All nitrates, acetates, and chlorate's (AgCH3COO only moderately)

4. All chlorides, bromides, and iodides EXCEPT those containing Ag+, Pb2+, and Hg2 2+ (moderately soluble in warm water)

5. All sulfates EXCEPT those containing Pb2+ or the 4 heavier ions of Group IIA ( Ca2+, Sr2+, Ba2+, Ra2+)

Low solubility

6. All sulfides EXCEPT those containing alkaline earths and rules 1 and 2

7. All hydroxides EXCEPT those containing Sr2+ and Ba2+ and rules 1 and 2

8. all phosphates, carbonates, and sulfites EXCEPT for rules 1 and 2

We then turned to page 14 and finished up problem number 3. This was about writing net ionic equations. First you have to present the ions that were present in each solution, and then you identify the solid that are being formed, and then indicate the ions remaining in the solution. And then at the end you write the net equation of the solution.

example a.

Na2SO4 + BaCl2

-ions: Na+ Cl+

-solid: Ba SO4

net ionic equation: Ba2+(aq) + SO4 2-(aq) ---> BaSO4(s)

example b.

AgNO3 + NaCl

-ions: Ag+ Cl+

-solid: Ag+ Cl+

net ionic equation: Ag+(aq) + Cl-(aq) ----> AgCl(s)

We then went on to finish the rest of the page. In problems 5-8 you had to analyze the major species in the solution and write the net ionic equations for the solutions.

5. Pb(ClO4)2(aq) + NaI (aq) ---> PbI2(s) + NaClO4(aq)

Pb2+(aq) + 2I-(aq) ----> PbI2(s)

6. Ca(OH)2(aq) + H3PO4(aq) ---> H2O(l) + Ca3(PO4)2(aq)

Ca2+(aq) + PO4 3-(aq) ----> Ca2(PO4)2

7. CdBr2 + Na2S ---> CdS(s) + 2 NaBr(aq)

Cd2+(aq) + S2+ (aq) ----> CdS(s)

8. NaOH + Fe(NO3)3 ----> Fe(OH)3 + NaNO3 (s)

Fe3+(aq) + 3H9aq) ---> Fe(OH)3 (s)

For problem 9, you are given a sentence which has the names of the solutions and you have to write them out and then write the net ionic equation.

9. Silver nitrate is mixed with sodium chloride solution

AgNO3(aq) + NaCl(aq) ----> AgCl(s) + NaNO3(aq)

net ionic equation: Ag+(aq) + Cl-(aq) ---> AgCl(s)

Some notes to keep in mind for the test....

-Aqueous solution of ionic compounds contain the compound in ion form.

-Ion charges can be found from....

.....the location on the periodic table for ions of the main group elements..

....the Roman numeral used in the name for ions of transition metal elements..

* when two aqueous solutions of ionic compounds are mixed, a precipitate can be formed; an ion from one of the solutions reacts with an ion from the other solution to form a solid precipitate.