Assignment directions for a project using water hardness
380 South Buzz Blvd
Bee Hive, UT 84302
The County Council of Governments would like to know how the total water hardness compares between various communities in the county. Some soft water costumers think their systems are being affected by excessive hard water provided by the community. The County Council of Governments has a budget of $60,000 to answer their question.
Before you begin your work, I will need the following information from you so that I can approve your work. The planning space for these items is found in your project packet.
Ø a detailed summary of your hypothesis, experimental
design table, a plan for the procedures along with all
necessary data tables
Ø a description of necessary calculations
Ø an itemized list of equipment with costs and chemical with
their costs, include labor costs of $80 / hour and cost for
laboratory space $10,000/day, and a standard disposal
fee of $2000 / gram of material.
After you complete the analysis, prepare a report for the County Council of Governments. Remember that this report will be seen by a variety of people, so be certain it projects the image we want to present. The items that should be included in the report are found in your project packet.
Good luck with the project. Please keep in close contact me as you proceed with the project. You will need a data verification signature, by having me observe one of the trials in the experiment.
President and CEO
CheMystery Labs Inc.
The Total Hardness Of Water In Local Water Supplies
Hard water contains dissolved salts, especially those of calcium and magnesium. Hard water often contains magnesium and
CaCO3 + H+ ---------> Ca2+ + HCO3-
The reaction of water with atmospheric carbon dioxide makes rain water naturally slightly acidic. Unnatural acidic
H2O + CO2 (g) ---------> H2CO3 (aq)
H2O + SO2 (g) ---------> H2SO3 (aq)
H2O + 2NO2 (g) ------------> HNO2 (aq) + HNO3 (aq)
The location of limestone deposits varies throughout the country, as do the amounts of industrial acids exposed to
Calcium ions, while nontoxic, present a number of significant household and industrial problems. For example,
Ca2+ + 2CH3(CH2)15COO-Na+ ----------> 2Na+ + (CH3(CH2)15COO-)2Ca
sodium stearate calcium stearate
Hard water also accounts for the buildup of "boiler scale" on the insides of teapots, water heaters, and industrial
Ca(HCO3)2 (aq) + heat ----------> CaCO3 (s) + CO2 (g) + H2O
The calcium carbonate scale must be removed periodically because it reduces heating efficiency by acting as an
The analysis for water hardness is based on the chemical reaction of Ca2+ ( and Mg2+) with an ion called
The analytical procedure is a titration. In this titration, a known amount of water is measured out and EDTA
solution is added drop-wise until just enough is present to completely react with all of the calcium and
magnesium ions in the sample.
In the project you will measure the total amount of calcium and magnesium ions in
The indicator is red in the presence of Mg2+. EDTA reacts with both Ca 2+ and Mg 2+. The indicator turns blue
You will report the results as either parts per million (ppm) of calcium carbonate, CaCO3, even though some of the
Experimental Procedures for measuring the
General Testing for Water Hardness
1. Add 2.5 mL of water to a 10 mL graduated cylinder
2. Add 6 drops of hardness #1 [ a buffer ]
3. Add 3 drops of hardness #2
4. Add drop by drop hardness #3 until the color
Types of tests that must be conducted
1. Test the color change of the indicator. Use 2.5 mL of distilled water to conduct this test.
2. Three trials of the calcium reference solution.
3. Three trials of each local water sample.
1. Calculate the average number of drops of EDTA used for each set of titrations.
2. Calculate the mg of hardness per drop of EDTA used for the reference solution.
.5 mg hardness in ref. sol'n X 2.5 mL of ref. sol'n = mg of hardness
3. Calculate the mg of hardness for each local water supply sample.
drops of EDTA X mg of hardness = mg of hardness
4. Finally, convert this into milligrams of hardness per liter of water. This is the normal way of reporting
** Every drop of hardness #3 = 1 grain of total hardness per gallon of water
Hardness #3-Titrate Solution
Calcium carbonate reference solution 500 mg / L or .5 mg / mL
Other Ideas for Water Hardness Research Projects
How effective are various water softeners at removing the total water hardness in our community?