Lab - Analysis of Water
Uploaded by erobinson on Apr 30, 2004
Analysis of Water
Introduction:
This lab will teach us how to identify several different substances that may be present in tap water and ocean water using different chemical tests. It will also show us the presence of solids in both tap water and ocean water.
[img:88464c657d]http://www.collegepimp.com/echeat/lab3.gif[/img:88464c657d]
Balanced Equations:
9. Test Tube #3: a) Ca + CO3 -> CaCO3 b) Mg + CO3 -> MgCO3
10. Test Tube #4: Ag+ + Cl- -> AgCl(s)
11. Test Tube #5: Ba + SO42- -> BaSO4
12. Test Tube #6: Pb + HCl -> PbCl2(s) + H+
Calculations:
Weight of Residue = (Original Weight) – (Weight after boiling)
151.734g – 151.726g = 0.008g
%Total solids in Tap Water = (Grams of residue) / (Grams of original solution)
0.008g/(223.238g-151.726g) = 0.008g/75.512g = 0.011%
ppm = (mg solute) / (Liters Solution)
8mg/(0.075L) = 100ppm
Discussion:
The purpose of part one of this experiment was to observe the presence of solids in the local tap or ocean water. To do this we boiled 75mL of tap water in a beaker. We compared the masses of the beaker before water was added, and after it was evaporated to determine the weight of the remaining residue. We obtained a light crusty brown residue at the bottom of our beaker. It was found to weight only 8mg, which means the local tap water has very little solids.
Still looking at tap water, part two was to determine the presence of several different elements. We used a variety of different chemical solutions and observed their reactions when added to tap water. The water contained no nitrate ions because there was no reaction with iron (II) sulfate and sulfuric acid. However, we did get to see what it would look like if nitrate was present because in one sample we added HNO3. Both calcium and magnesium were present because when added ammonium carbonate to our sample it formed calcium carbonate and magnesium carbonate as can be seen in the following balanced equations: Ca + CO3 -> CaCO3, Mg + CO3 -> MgCO3. Chloride was also present because when we added nitric acid and silver nitrate, silver chloride was formed as can be seen in the balanced equation: Ag+ + Cl- -> AgCl(s). Sulfate was also present because when we added barium nitrate, barium sulfate was formed as can be seen in the balanced equation: Ba + SO42- -> BaSO4. Lead was...