The purpose of this experiment is to analyze four drinking water samples from different places using four of the standard drinking water tests required by the EPA. The experiment will be performed by a four person group, with each person providing a different water sample. The four tests to be performed are: pH, conductivity, phenolphthalein and total alkalinity, and total and non-carbonate hardness. Data from these four tests will be gathered and analyzed, drawing conclusions “about the validity of the data as well as the quality of water” (Kippenhan 137). All of the techniques that will be used in this lab have already been learned in previous experiments. These tests are important; drinking water must meet certain standards of these tests to be considered drinkable.
4 Drinking water samples from different sources
1 250mL Erlenmeyer flask 1 150mL beaker 1 250mL beaker 1 50mL volumetric pipette
Test #1 – pH
Laptop with Logger Pro Chemicals:
pH probepH 4 buffer solution
3 10 mL beakers pH 7 buffer solution 1 support stand and clamp pH 10 buffer solution
Test #2 – Conductivity
Equipments/Glassware: Chemicals: Laptop with Logger ProNaCl std. soln. (lowconductivity)
Conductivity probe and Switch boxNaCl std. soln. (med. conductivity) 2 10mL beakers
Test # 3 – Phenolphthalein and Total Alkalinity
1 support stand and buret clamp Phenolphthalein indicator 50mL buret
1 50 mL volumetric pipette 0.010 M HCl 1 short stem funnel 10% Thiosulfate indicator Glass stirring rod Bromocresol green indicator Test #4 – Total Hardness
Equipment/Glassware: Chemicals: 1 support stand 0.01M EDTA
buret clamp Univer3 indicator
50 mL volumetric pipette
Na2H2Y(aq)+Mg2+MgY2-(aq)+ 2H+(aq)+2Na+(aq) (Y=EDTA molecule) Safety Precautions:
Wear safety goggles. HCl is toxic and corrosive. Avoid contact with skin, eyes, and clothing. Procedure:
1. If the test is not already set up, turn on computer, open the 1290 folder, and select Exp. 24 Acid/Base Titration. 2. Calibrate the pH probe using a two-point calibration using pH 4 and 7 buffers. 3. Analyze each sample’s pH twice.
4. Calculate the [OH-] for each pH reading.
1. If the test is not already set up, turn on computer and select Exp. 14 Conductivity on the desktop. Make sure the switch box is set to 0-2000 μS/ cm. 2. Calibrate the conductivity probe using a two-point calibration using the low and mid-range solutions. 3. Analyze each sample’s conductivity two times. Report the amount of TDS in each sample in mg/L and ppm.
Total and Phenolphthalein Alkalinity tests:
1. Use volumetric pipette to obtain 50 mL of water sample. Add 3-5 drops phenolphthalein. 2. Titrate sample with HCl to a colorless endpoint. Record the initial and final volume of HCl in the burette. 3. Add a few drops of 10% thiosulfate solution and 3-5 drops of bromocresol green/ methyl red. 4. Titrate the sample to a faint straw-colored endpoint. 5. Report phenolphthalein alkalinity and total alkalinity in molarity and ppm. 6. Repeat steps 1-5 for the remaining 3 water samples.
Total Hardness Test:
1. Use volumetric pipette to measure 50 mL of water sample. Add 5 scoops of UniVer3 indicator to the sample. The color should be red/pink. 2. Titrate the sample using EDTA until the color of the solution changes to a light...