The Color of Chemistry Teacher Notes
Lab Time: 50+ minutes
TIME: 15 minutes
T: Provide goggles, gloves, and aprons. Make sure lab is put away properly.
V: Will provide complete lab.
PO43- I1- SO42- CO3-2 SiO32- OH1- HCO31- Cl1- Br1- Fe(CN)63- C2O42- SO32-
Ag+1 Yellow Cream White White Lt yellow Brown Cream White White Yel/Orange White NR
Co+2 Lavender NR NR Lavender Purple Gray Pink NR NR Magenta Lavender NR
Fe+3 White Orange NR Orange Peach Orange Orange NR NR Red/brown Tan NR
Ni+2 Green NR Green Green Green Green NR NR Yel/orange Blue NR
Cu+2 Blue Brown NR Blue Turquoise Blue Turquoise NR NR Tan Blue NR
Mn+2 Gray NR Green Rose Red Brown Rose NR NR Dk. Brown Pink Red
Ba+2 White Orange White White White White White NR NR Yellow White White
Cu+1 NR Yellow NR Lt. Blue Lt. Blue Lt. Blue Lt. Blue NR NR Yellow Lt. Blue NR
Answers to Questions:
1. Take a look at your observations and determine what if any generalizations you
can make about any of the horizontal or vertical rows. For example: In the
sodium nitrate row, a typical observation might be this statement: “All nitrates
All nitrates, acetates, and ammonium compounds are soluble. All bromides,
chlorides, and iodides are soluble with the exceptions of compounds containing
the heavy metals Co, Hg, and Ag. In addition, BaI2 and CuI2 are insoluble. The
sulfates are soluble with the exceptions of BaSO4, Hg2SO4, HgSO4, CoSO4,
CaSO4, and Ag2SO4. The carbonates, sulfides, phosphates, and hydroxides are
ASIM The Color of ChemistryTeacher Notes p. 1
insoluble with the exceptions of those of ammonium ion and alkali metals (Na
2. Define the term “solubility product”. Give an example, using one of the
precipitates from the data table and the concentrations. Show how you know that
this substance should form a precipitate. Write net ionic equations for all the
reactions that resulted in a gas or precipitate.
The solubility product, Ksp, is the equilibrium constant that applies to the
dissolution of a slightly soluble compound. It is equal to the product of the
saturated concentrations of the constituent ions, each raised to the power which
corresponds to the number of ions in one formula unit. To see if a precipitate
should occur, one would evaluate the reaction quotient, Q, where Q has the same
form as Ksp. For example, Ag2S would have a Ksp = [Ag+][S2-]2 = 5.5 x 10 -51 .
Since our solutions were 0.1 M and become approximately 0.05 M upon dilution
with the other solution, Q = [Ag+][S2-]2 = [.05][.05] 2 = Q = 1.25 x 10-4. Since Q >
Ksp, a precipitate should form.
This experiment was taken from a workshop presented by John Malch and the lab he
wrote up was titled “Can you make your own paint pigments?”
ASIM The Color of ChemistryTeacher Notes p. 2