Water Hardness Essay Example for Free

Water Hardness EssayMETHODS1. Prepare an approximate 0.004 M disodium EDTA solution. To prepare this solution, weigh about 0.7-0.8 g of Na2EDTA and crash in 500 mL deionized water in your plastic bottle. Make to to shake the bottle to dissolve the salt. 2. Obtain a 250-mL Erlenmeyer flask and transfer a 10 mL of CaCO3 using a buret into the flask. 3. Measure 30 mL of deionized water and add it into the titration flask. 4. Make sure to stir the solution5. inwardly a fume hood, add 3mL of ammonia/ammonium chloride buffer (pH10) into the flask and stir for another 30 seconds. 6. add up four drops of Eriorchrome Black T index number solution. nurture for another 30 seconds 7. Begin titration. Record your initial volume and final volume. At the endpoint, the color will change to pink to violet to blue. 8. ring this titration two more times. Now that you recorded the volume, your second and third visitation should be a lot easier.9. Take your water sample that you obtain from t he stock room and record the unknown number. 10. Transfer 25 mL of the unknown water sample to a 250-mL Erlenmeyer flask. 11. Add about 20 mL of deionized water to the titration flask. Stir for 30 seconds 12. Inside a fume hood, add about 3 mL of ammonia/ammonium chloride buffer (pH10) and stir for another 30 seconds. 13. Add four drops of Eriorchrome Black T indicator solution to your flask and stir for 30 seconds. 14. Begin titrating. Record you initial volume and final volume. Repeat this double more. Calculate the average hardness and your experimental precision from the three trials.RESULTSEDTA Solution0.7533g of Na2EDTA mixed with 500ml DI waterTable A Standardization of EDTATrial Start hoi polloi End Volume Amount of EDTA1 3.90ml 29.85ml 25.95ml2 5.35ml 28.35ml 23.00ml3 0.45ml 23.50ml 23.05mlMoles EDTA calculations first and 3rd trial(10.1 mL CaCO3) x (1L/1000ml) x 1.000g CaCO3/1L) x (1 mole CaCO3/100.1 g CaCO3) x (1 mole EDTA / 1 mole CaCO3) x (1000ml/L) = 0.101moles EDTA/L 2nd trial(9.90 ml CaCO3) x (1L/1000mL) x (1.00 g CaCO3/L) x (1 mole CaCO3/100.1g CaCO3) x (1 mole EDTA/1 mole CaCO3)x (1000 mL/1L) == 0.099 moles EDTA/LMean molarity(0.101 + 0.099 + 0.101)/3 = 0.100 moles EDTA / LWater hardness calculationsUnknown water sample 24Table 2. Water sampleTrial EDTA Water sample 241 13.45ml 25.1ml2 13.35ml 25.5ml3 13.50ml 25.0mlCaCO3 molar mass 100.1g/mole1st trial(13.45 mL EDTA/25 mL of unknown water sample) x (1L/1000mL) x (0.101 molesEDTA/1L) x (1mole CaCO3/1 mole EDTA) x (100.1 g CaCO3/1 mole) x (1000 mg CaCO3/1g) x (1000mL/1L) == 5439.2 mg CaCO3/1L2nd trial(13.35 mL EDTA/25 mL of unknown water sample) x (1L/1000mL) x (0.099 moles EDTA/1L) x (1mole CaCO3/1 mole EDTA) x (100.1 g CaCO3/1 mole) x (1000 mg CaCO3/1g) x (1000mL/1L) == 5291.9 mg CaCO3/1L3rd trial(13.50 mL EDTA/25 mL of unknown water sample) x (1L/1000mL) x (0.101 moles EDTA/1L) x (1mole CaCO3/1 mole EDTA) x (100.1 g CaCO3/1 mole) x (1000 mg CaCO3/1g) x (1000mL/1L) == 5459.5 mg CaCO3/1LCalcu late the total hardness in ppm CaCO31st trial13.45ml EDTA x (0.004M/1000ml) x (100.1g CaCO3/1mole CaCO3) x (1000mg CaCO3/1g CaCO3) x (1000L/25.1ml) = 214.6 ppm CaCO32nd trial13.35ml EDTA x (0.004M/1000ml) x (100.1g CaCO3/1mole CaCO3) x (1000mg CaCO3/1g CaCO3) x (1000L/25.5ml) = 209.6 ppm CaCO33rd trial13.50ml EDTA x (0.004M/1000ml) x (100.1g CaCO3/1mole CaCO3) x (1000mg CaCO3/1g CaCO3) x (1000L/25ml) = 216.2 ppm CaCO3Average ppm (216.2 + 209.6 + 214.6)/3 = 213.5ppmCONCLUSIONThe concentration was concluded to be 213.5 ppm in the unknown which is right about in between genus Phoenix water hardness which is 164-291 ppm.REFERENCEDepartment of Chemistry.(2012,February).Complexometric Determination of Water Hardness.Mesa ArizonaCity of Phoenix Official Websitehttp//phoenix.gov/waterservices/quality/index.html