Chemistry 121
Prof. Mines
PS6 Sheet
Reading Assignment: Sections 4.4-4.9
Problem Set #6
1. 4.60 [4.62 in Mast]; 2. 4.62 [4.64 in Mast]; 3. 4.63 [4.65 in Mast];
4. NT1; 5. NT2; 6. NT3
(Molarity [Dilution], Stoichiometry w/ Molarity)
(Nanoscopic pics of ionic compounds, Molarity of Ions (in Strong Electrolyte solutions)
7. 4.67 [4.71 in Mast]; 8. 4.70 [4.74 in Mast]; 9. 4.69 [4.73 in Mast]; (Electrolytes, Solubility Rules, Ions in SE solutions)
10. NT4;
(Predicting the products in a potential exchange [precipitation] reaction) **PS3 ideas applied!**
11. NT5; 12. NT6;
13. NT7;
(Nanoscopic representation of precipitation reaction, Net Ionic Equations (NIE’s)
(Predicting the products in a potential exchange [acid-base] reaction, NIE’s) **PS3 ideas applied!**
14. 4.84 [4.88 in Mast];
(Titration, Stoichiometry with Molarity)
15. 4.88 [4.92 in Mast]; 16. 4.90 [4.94 in Mast]; 17. NT8;
(Oxidation Numbers, Redox Language)
18. 4.92 [4.96 in Mast]; 19. 4.91 [4.95 in Mast]; 20. NT9;
(Identifying Redox Reactions, Redox Language)
21. NT10; 22. MP (a Mastering Problem not in text)
(Cumulative Stoichiometry/Molarity/L.R./%Yield/EF Problems)
NT1. (a) Draw a picture of a sample of solid sodium carbonate containing four formula units of compound. Draw
the atoms as shown below. Note that you need to decide whether or not the compound is molecular or ionic
before you can draw a meaningful picture. You may wish to draw a "simpler" compound (like sodium sulfide)
first on a separate sheet of paper to help you.
(b) Draw a snapshot of your compound after it has dissolved in a beaker of water. Do not draw the water
molecules—just represent how the sample of compound would look in the solution. Make sure that your
second picture has the same amount of compound in it as is depicted in the solid piece that you drew in part
(a). Use the depiction below as a guide for what to write on your homework paper (or you can just write on
this page):
Na atom (or ion) =
solid sodium carbonate (4 formula units)
C atom =
O atom =
4 formula units of sodium carbonate dissolved in water
NT2. In each of the following solutions, calculate the concentration (in M) of i) the solute (i.e., the
compound dissolved), ii) the cation, and iii) the anion (E.g., in the first one, calculate [Na3PO4],
[Na+], and [PO43-] in the solution described)
(a) 0.0200 mol of Na3PO4 dissolved in 10.0 mL of solution
(b) 132 g of (NH4)2SO4 dissolved in 1.50 L of solution
NT3. Calculate the sodium ion concentration in a solution formed by mixing 70.0 mL of 3.0 M Na2CO3 with
30.0 mL of 1.0 M NaHCO3. (Assume the final volume of the solution is 70.0 mL + 30.0 mL)
NT4. Do Tro, problem 4.74(all parts), and then add the following equation as part (e)
(e)
Fe(NO3)3(aq) + Na2S(aq) 
Chemistry 121
Prof. Mines
NT5 Given the following equation: 2 CsF(aq) + CaCl2(aq)  CaF2(s) + 2 CsCl (aq),
(a) Draw a representation of what a solution with 8 formula units of CsF and a solution with 5 formula units
of CaCl2 would look like, and then draw what a beaker would look like if the two solutions were mixed
and the reaction was allowed to proceed to completion. Write the correct number and proper depiction of
all species. Use the symbols below in your pictures.
Cs+ =
F =
Ca2+ =
X
Cl =
X
mix
8 F.U. CsF(aq)
5 F.U. CaCl2(aq)
after mixing and reaction is complete
(b) Write the net ionic equation representing the reaction that occurred, and then describe in words what
actually occurs (changes) during this reaction.
NT6 4.75(d) & 4.76(d) in Tro
NT7. Complete the following equations (i.e., write proper formulas for the products), and then write the
balanced (i) molecular, (ii) complete ionic, and (iii) net ionic equations for each. If no reaction occurs,
write NR.
(d) The equation in Tro, 4.81(c)
(e) The equation in Tro, 4.82(b)
(a) HNO3(aq) + Al(OH)3(s) 
(b) KC2H3O2(aq) + H2SO4(aq) 
(c) NaNO3(aq) + HCl(aq) 
NT8. For each of the following kinds of chemical species, state whether the oxidation number increases or
decreases when a redox reaction takes place. Reasoning must be provided!
(a) An oxidizing agent
(b) A species undergoing oxidation
(c) A species that gives away electrons
(d) A species undergoing reduction
(e) A species that accepts (gains) electrons
(f) A reducing agent
NT9. (i) Identify the oxidizing agent and reducing agent in each reaction depicted by a chemical equation below
(How? By assigning oxidation #’s to all atoms in all reactants and products. SHOW THIS WORK).
(ii) State which species gets oxidized, and which species gets reduced when reaction occurs in each case.
(iii) State which species takes (i.e., gains) electrons, and which species gives (i.e., loses) electrons in each
case.
(a) 2 Na(s) + 2 H2O(l)  2 NaOH(aq) + H2(g)
(b) 2 I2(s) + IO3 (aq) + 10 Cl(aq) + 6 H+(aq)  5 ICl2 (aq)** + 3 H2O(l)
(**Assign Cl an oxidation number of -1 in ICl2 (aq) )
NT10. Carminic acid, a naturally occurring red pigment extracted from the cochineal insect, contains only
carbon, hydrogen, and oxygen. It was commonly used as a dye in the first half of the nineteenth century.
It is 53.66% C and 4.09% H by mass. A titration required 18.02 mL of 0.0406 M NaOH to neutralize
0.3602 g carminic acid. Assuming that there is only one acidic hydrogen per molecule (i.e., it has a generic
th
formula “HA”), what is the molecular formula of carminic acid? (This problem is from Zumdahl, 7 edition)
Hint: Use the titration information first to determine the molar mass. Then use the %mass info.