CHM421 Experiment 5 Distillation and Hardness of Water PDF

Preview

Summary

LABORATORY REPORTANALYTICAL CHEMISTRY (CHM421)Title of the experiment EXPERIMENT 5: DISTILLATION AND HARDNESS OF WATERName NORSYAZANA IZZATI BINTI NORAZAMIID Number 2021125545Class AS24643BLecturer’s Name DR. MOHD AZRI AB RANIFACULTY OF APPLIED SCIENCEABSTRACTIn this experiment, the aims and objecti...

Description

LABORATORY REPORT ANALYTICAL CHEMISTRY (CHM421) Title of the experiment

EXPERIMENT 5: DISTILLATION AND HARDNESS OF WATER

Name

NORSYAZANA IZZATI BINTI NORAZAMI

ID Number

2021125545

Class

AS24643B

Lecturer’s Name

DR. MOHD AZRI AB RANI

FACULTY OF APPLIED SCIENCE

ABSTRACT In this experiment, the aims and objectives were to purify water sample by distillation, standardize the EDTA solution and to analyze the hardness of water samples by titration with EDTA. The first thing that has been done was the water sample was distillated until the required amount was produced. The temperature at start of collecting the distillate is 96 oC. The temperature at the end of collecting the distillate is 99 oC. Next, the concentration of EDTA solution was obtained through standardization against Ca 2+ solution, which is 4.94 x 10 -3 M. Lastly, the standard EDTA solution was titrated to the different water sample that contains buffer and indicator, and the volume of EDTA solution was recorded. The data collected was used to calculate the hardness of the water in term of ppm unit. The hardness of Lab Tap Water, Lab Distilled Water, Home Tap Water, Distilled Home Tap Water, 0.1 M NaCl and Deionized Water.

OBJECTIVES 1. To purify water sample by distillation 2. To standardize EDTA solution 3. To analyze hardness of water samples by titration with EDTA

INTRODUCTION In this experiment, we will carry out the most common purification method for liquids, distillation. Home tap water will be distilled and then the hardness of the original tap water will be compared to that of the distilled water and the other water samples to determine the effectiveness of the distillation procedure. Today’s experiment will make use of the one of the four types of volumetric method of analysis, i.e., the complexation titration to determine the hardness of water sample. We may have heard of the term hard water and soft water. Can water be hard? Hard here does not mean literally but rather it has a different and special meaning when applied to water. Hardness is a measure of the total amount of calcium and magnesium salts present in the water. Since soap is consists of fatty acid salts and the fatty acid salts of calcium and magnesium are insoluble in water (scum), the effectiveness of the soap decreases as hardness increases due to precipitation with magnesium and calcium. Thus, we need to use more soap or detergent to do the cleaning job if the water is hard. And because of the precipitation form, hard water will cause a layer of calcium carbonate on the heating coil of the kettle and thus will require more time to boil the water. In this experiment, we use the method of the titration which is a very commonly used quantitative analysis technique and is easily applicable here to determine the total hardness (amount of calcium and magnesium ions) in some water samples.

Distillation Distillation is probably the most commonly used technique for the purification of liquids. Distillation technique requires the input of energy to convert a liquid to its vapor and then condensation of the vapor to liquid in another part of the distillation apparatus. Impurities with low boiling point will vaporize and condense first and can be collected and put aside. High boiling point impurities on the other hand will remain in the distilling flask unless more heat is provided. Boiling will occur when the vapor pressure of the substance equals to the confining pressure. When the confining pressure is at atmospheric pressure, we call the temperature at which boiling occu rs the normal boiling points. There are many parameters that contribute to the efficiency of the separation. These include the length and packing of the distilling column, the distillation rate, and the confining pressure. What we sill be doing today is just a simple distillation at atmospheric pressure. Water Softeners and Ion Exchange Apart from distilling water to separate impurities and thus reduce the hardness, water hardness can also be reduced b replacing the calcium and magnesium ions in the water sample by other ions. Home water softeners usually replace calcium and magnesium ions with sodium ions. Other cation exchange resins replace the cations in the water sample with hydrogen ions. Anion exchange resins usually replace anions with chloride or hydroxide ions. If both hydrogen and hydroxide resins were used, hydrogen and hydroxide ions are produced which then react with each other to yield water. Water purified by this method is called deionized water. This is an excellent technique for the purification of water compared to distillation and is now more commonly used to purify water for chemistry labs. Complexometric Titration We can determine the total amount of calcium and magnesium in the water by titrating the sample with a standard solution of ethylenediaminetetraacetic acid (EDTA). Hardness is more commonly expressed in unit of ppm rather than molarity because of the low concentration value.

PROCEDURE A. Distillation of the Home Tap Water A typical distillation apparatus was set up using the 150 mL round bottom flasks for the distilling flasks and a 250 mL conical flask for the receiver to collect the distillate. All the apparatus were clamped adequately and placed at strategic places to avoid breakages. The distilling water was filled to about two-thirds with home tap water. A couple of boiling chips were added to the flasks to prevent bumping. We turned on the tap and checked the water flows uphill in the condenser.

The mercury bulb of the thermometer was inspected to ensure it was slightly lower than the junction of the condenser with the distillation column. The distillation flask was heated gently and cautiously with a Bunsen flame. After the water was boiled, the liquid can be collected. The first 20 drops of the distilled water collected should be discarded as they might contain volatile impurities and the impurities from the distillation glassware. The temperature of the distilling flask was recorded as we start to collect 1 mL of the distillate. The distillate was collected until there are about 5 mL of the liquid left in the distillation flask. At the point the distillation was stopped, the temperature in the distilling flask was recorded. Then, the burner was turned off. B. Standardization of the EDTA solution In part B of this experiment, we needed to standardize the EDTA solution through titration. A 50 mL of burette was cleaned and rinsed thoroughly with distilled water, then drained the distilled water into a waste beaker. Next, the burette was rinsed with the EDTA solution, and the rinses were disposed of out of the burette. The EDTA solution was poured into the burette beyond the zero marks. The burette was attached to a burette stand. After removing all the bubbles, the initial reading was adjusted but did not have to be zero. The outside of the burette tip was wiped to remove any adhering liquid there. 25.0 mL of aliquots of the prepared standard Ca2+ solution was pipette and transferred to a 250 mL conical flask. The concentration of the CaCO 3 prepared was recorded. Next, 8 mL of pH 10 ammonia-ammonium chloride buffer, 15 mL of distilled water and 3 drops of Eriochrome Black T indicator were added into the flask. The sample was titrated immediately with the EDTA solution against a white background until the light pink turns to light sky blue. The volume of the burette at the endpoint was recorded. The whole process was repeated with at least two more samples. C. Water Hardness For part C, the hardness of the water. The burette was filled up with more EDTA solution. A 25 mL pipette was rinsed with tap water, and 25.0 mL of lab tap water was pipette into a 250 mL conical flask. 8 mL of pH 10 ammonia-ammonium chloride buffer and 3 drops of Eriochrome Black T indicator were added into the water sample in the flask. The initial burette was recorded to the nearest 0.01 mL. The standard EDTA solution in the burette was added carefully to the water sample in the flask. When the formation of blue color appeared in the solution, the addition of titrant was slowed down to dropwise addition. The titration was stopped at the first color change observed in the flask. The final burette reading was recorded, and the titration was repeated with another water samples. A little bit of lab distilled water was obtained using the rubber filler. The filler was removed, tilted and the pipette was rotated to rinse the inside of the pipette with the distilled water. The tainted distilled water was thrown away. 25.0 mL of fresh distilled water was pipette into a clean but not necessarily dry flask. Buffer and indicator were added as above step and titrated with the standardized EDTA solution. Repeated. The pipette with home tap water or an unknown was rinsed. 25.0 mL of the unknown was pipette into a clean flask. Buffer and indicator were added into the flask, and the sample was titrated with standardized EDTA solution. The method for the rest samples above was repeated, and all the data was recorded.

RESULTS A. Distillation of home tap water 1. Temperature at the start of collecting the distillate = 96.0 °C 2. Temperature at the end of collecting the distillate = 99.0 °C 3. Experimental boiling range for collected sample = 97.5 °C

B. Standardization of the EDTA solution Concentration of standard Ca2+ solution = 0.007 M Volume of the standard Ca2+ solution = 25.0 ml

Rough

1

2

Final reading of EDTA solution

37.50

35.75

35.55

Initial reading of EDTA solution

0.10

0.15

0.20

Volume of EDTA solution (mL)

37.40

35.60

35.35

C. Hardness of Water Concentration of EDTA = 4.94𝑥10−3M Water sample

Lab tap water

Lab distilled water

Home tap water

Distilled home tap water

Deionized water

0.1 M NaOH

Final reading of standard EDTA

2.00

4.00

1.85

0.30

9.90

10.85

Initial reading of standard EDTA

0.10

2.10

0.20

0.10

4.10

10.00

Volume of standard EDTA used (ml)

1.90

1.90

1.65

0.20

5.80

0.85

Volume of water sample (ml)

25.0

25.0

25.0

25.0

25.0

25.0

[Ca2+ + Mg2+] (mol/L)

3.75 x 10-4

3.75 x 10-4

3.26 x 10-4

3.95 x 10-5

1.15 x 10-3

1.68 x 10-4

37.58

37.58

32.63

3.95

115.10

16.82

Hardness (ppm)

B. Standardization of the EDTA Solution 𝑅𝑜𝑢𝑔ℎ 𝑀1𝑉1 = 𝑀2𝑉2 𝑀1(37.40 𝑚𝐿) = (0.007 𝑀)(25.0 𝑚𝐿 ) 𝑀1 = 4.68𝑥10−3 𝑀 𝑇𝑟𝑖𝑎𝑙 1 𝑀1𝑉1 = 𝑀2𝑉2 𝑀1(35.60𝑚𝐿 ) = (0.007 𝑀)(25.0 𝑚𝐿) 𝑀1 = 4.92𝑥10−3 𝑀

𝑇𝑟𝑖𝑎𝑙 2 𝑀1𝑉1 = 𝑀2𝑉2 𝑀1(35.35 𝑚𝐿) = (0.007 𝑀)(25.0 𝑚𝐿 ) 𝑀1 = 4.95𝑥10−3 𝑀 4.92𝑥10−3 + 4.95𝑥10−3 2 𝐴𝑣𝑒𝑟𝑎𝑔𝑒 𝑚𝑜𝑙𝑎𝑟𝑖𝑡𝑦 𝑜𝑓 𝐸𝐷𝑇𝐴 = 4.94𝑥10−3𝑀 𝐴𝑣𝑒𝑟𝑎𝑔𝑒 𝑚𝑜𝑙𝑎𝑟𝑖𝑡𝑦 𝑜𝑓 𝐸𝐷𝑇𝐴 =

C. Hardness of Water 𝑳𝒂𝒃 𝑻𝒂𝒑 𝑾𝒂𝒕𝒆𝒓 𝑀1𝑉1 = 𝑀2𝑉2 𝑀1(25.0 𝑚𝐿 ) = ( 4.94𝑥10−3𝑀)(1.90 𝑚𝐿 ) 𝑀1 = 3.75𝑥10−4𝑀 𝑚𝑔 𝐿 100.09𝑔𝐶𝑎𝑐𝑂3 1000𝑚𝑔 −4 = 3.75𝑥10 𝑀 𝑥 𝑥 1𝑔 1 𝑚𝑜𝑙 = 37.58 𝑝𝑝𝑚 𝐻𝑎𝑟𝑑𝑛𝑒𝑠𝑠 = 𝑝𝑝𝑚 =

𝑳𝒂𝒃 𝑫𝒊𝒔𝒕𝒊𝒍𝒍𝒆𝒅 𝑾𝒂𝒕𝒆𝒓 𝑀1𝑉1 = 𝑀2𝑉2 𝑀1(25.0 𝑚𝐿 ) = ( 4.94𝑥10−3𝑀)(1.90 𝑚𝐿 ) 𝑀1 = 3.75𝑥10−4𝑀 𝑚𝑔 𝐿 1000𝑚𝑔 100.09𝑔𝐶𝑎𝑐𝑂 3 𝑥 = 3.75𝑥10−4𝑀 𝑥 1 𝑚𝑜𝑙 1𝑔 = 37.58 𝑝𝑝𝑚 𝐻𝑎𝑟𝑑𝑛𝑒𝑠𝑠 = 𝑝𝑝𝑚 =

𝑯𝒐𝒎𝒆 𝑻𝒂𝒑 𝑾𝒂𝒕𝒆𝒓 𝑀1𝑉1 = 𝑀2𝑉2 𝑀1(25.0 𝑚𝐿 ) = ( 4.94𝑥10−3𝑀)(1.65 𝑚𝐿 ) 𝑀1 = 3.26𝑥10−4𝑀 𝑚𝑔 𝐿 1000𝑚𝑔 100.09𝑔𝐶𝑎𝑐𝑂 3 𝑥 = 3.26𝑥10−4𝑀 𝑥 1 𝑚𝑜𝑙 1𝑔 = 32.63 𝑝𝑝𝑚 𝐻𝑎𝑟𝑑𝑛𝑒𝑠𝑠 = 𝑝𝑝𝑚 =

𝑫𝒊𝒔𝒕𝒊𝒍𝒍𝒆𝒅 𝑯𝒐𝒎𝒆 𝑻𝒂𝒑 𝑾𝒂𝒕𝒆𝒓 𝑀1𝑉1 = 𝑀2𝑉2 𝑀1(25.0 𝑚𝐿 ) = ( 4.94𝑥10−3𝑀)(0.20 𝑚𝐿 ) 𝑀1 = 3.95𝑥10−5𝑀 𝑚𝑔 𝐿 100.09𝑔𝐶𝑎𝑐𝑂 1000𝑚𝑔 3 = 3.95𝑥10−5𝑀 𝑥 𝑥 1 𝑚𝑜𝑙 1𝑔 = 3.95 𝑝𝑝𝑚 𝐻𝑎𝑟𝑑𝑛𝑒𝑠𝑠 = 𝑝𝑝𝑚 =

𝑫𝒆𝒊𝒐𝒏𝒊𝒛𝒆𝒅 𝑾𝒂𝒕𝒆𝒓 𝑀1𝑉1 = 𝑀2𝑉2 𝑀1(25.0 𝑚𝐿 ) = ( 4.94𝑥10−3𝑀)(5.80 𝑚𝐿 ) 𝑀1 = 1.15𝑥10−3𝑀 𝑚𝑔 𝐿 1000𝑚𝑔 100.09𝑔𝐶𝑎𝑐𝑂 3 𝑥 = 1.15𝑥10−3𝑀 𝑥 1 𝑚𝑜𝑙 1𝑔 = 115.10 𝑝𝑝𝑚 𝐻𝑎𝑟𝑑𝑛𝑒𝑠𝑠 = 𝑝𝑝𝑚 =

𝟎. 𝟏 𝑴 𝑵𝒂𝑪𝒍 𝑀1𝑉1 = 𝑀2𝑉2 𝑀1(25.0 𝑚𝐿 ) = ( 4.94𝑥10−3𝑀)(0.85 𝑚𝐿 ) 𝑀1 = 1.68𝑥10 −4𝑀 𝑚𝑔 𝐿 100.09𝑔𝐶𝑎𝑐𝑂 1000𝑚𝑔 3 = 1.68𝑥10−4𝑀 𝑥 𝑥 1 𝑚𝑜𝑙 1𝑔 = 16.82 𝑝𝑝𝑚 𝐻𝑎𝑟𝑑𝑛𝑒𝑠𝑠 = 𝑝𝑝𝑚 =

DISCUSSION From this experiment, we gained the results from the calculation made. In the part B, we calculated the concentration or average molarity of the EDTA solution which is 4.94 x 10 -4 M. By using the average molarity gained from the calculation and the volume of EDTA solution gained from the table of data, the concentration of magnesium and calcium can be calculated. Next, the hardness of water of each water sample was determined and has been expressed in ppm unit. Hardness of water can be defined as the measurement of the total amount of calcium and magnesium salts present in the water. If the water has a high amount of magnesium and calcium in it, the hardness also increased. The calculation of the hardness of water was made. The result has been recorded in the table of data which are 37.58 ppm for Lab Tap Water and Lab Distilled Water, 32.63 ppm for Home Tap Water, 3.95 ppm for Distilled Home Tap Water, 115.10 ppm for Deionized water and 16.82 ppm for 0.1 M NaCl. The deionized water supposed to have a low hardness range since deionized water has low amount of calcium and magnesium salts present in the water. The hardness can be specified into 4 categories which is soft (0-60 ppm), medium hard (60-120 ppm), hard (120180 ppm) and very hard (above 180 ppm). So, the deionized water can be categorized as a mediumhard type of water. From the result that gained and calculated, some error might have occurred during the experiment. the error that occurred has been affecting the accuracy and precision of the result and data gained in the table of data. The error that might has been occurred was during the titration process that affecting the endpoint. A rough titration can be made before the actual titration to avoid the same error occur in the future. A rough titration helps in determining the approximate endpoint of the titration. Other than that, the error also can occur during the observing and taking the reading of the solution. this error also called as parallax error. We can avoid the inaccuracy of reading by ensuring that our eyes are perpendicular with the apparatus before taking the reading.

CONCLUSION In the conclusion, the objective of the experiment which are to purify water sample by distillation, standardize EDTA solution, analyze hardness of water samples by titration with EDTA has been achieved. The experiment is successful. The experimental boiling range for the collected sample was 97.5 oC. the concentration or average molarity of the EDTA solution was 4.94 x 10 -3. And lastly, the hardness of each water samples which are 37.58 ppm for Lab Tap Water and Lab Distilled Water, 32.63 ppm for Home Tap Water, 3.95 ppm for Distilled Home Tap Water, 115.10 ppm for Deionized water and 16.82 ppm for 0.1 M NaCl.

QUESTIONS 1. Why should the water in the condenser flow uphill during distillation? •

The water in the condenser flowing uphill during distillation to avoid and prevent the condenser from becoming too hot in its inner surface that can cause the distillate will come out of the system as vapor.

2. Compare the hardness between i) lab tap water and lab distilled water ii) home tap water and home distilled tap water. Did the distillation have a significant effect on the water hardness? Explain your answer. •

The Lab Tap Water and Lab Distilled Water has the same hardness. The Home Tap Water hardness is higher than the Home Distilled Tap Water. Yes, the distillation has a significant effect on the water hardness which is the impurities that has been removed from the water samples. Different impurities have different boiling point, so, the number of impurities removed from each sample are varies.

3. Water with hardness in the range 0-60 ppm is termed soft, 60-120 ppm is medium hard, 120180 ppm is hard and above 180 ppm is very hard. Classify the water samples that you analyzed in the experiment. Termed Soft (0-60 ppm) Lab Tap Water Lab Distilled Water Home Tap Water Distilled Home Tap Water 0.1 M NaCl

Medium-hard (60120 ppm) Deionized Water

Hard (120-180 ppm)

Very Hard (above 180 ppm)

4. Do you think there should be a correlation between conductance and hardness results? Explain your answer. •

Yes, there is a correlation between conductance and the hardness result. It is because as the conductance increase, the hardness of water also increases. The conductivity increases because of the increasing ion content, while the hardness also increases when the amount of calcium and magnesium ion increase.

5. Suggest any ways you can think of to improve any parts in this experiment. The experiment should be repeated at least once to ensure that the value of the titre that was obtained was accurate. •

In order to improve the accuracy of the hardness of water in part C, a multiple titration should be done to obtain a precise end result for each water sample. Other than that, we should be careful while doing the titration process as if the endpoint was slightly beyond may be resulting in the volume of the titrant too large.

REFERENCES Belle-Oudry, Deirdre. "Quantitative analysis of sulfate in water by indirect EDTA titration." Journal of chemical education 85.9 (2008): 1269. Diehl, Harvey, Charles A. Goetz, and Clifford C. Hach. "The versenate titration for total hardness." Journal‐American Water Works Association 42.1 (1950): 40-48. Diskant, Eugene M. "Stable indicator solutions for complexometric determination of total hardness in water." Analytical Chemistry 24.11 (1952): 1856-1857. Fritz, James S., J. P. Sickafoose, and M. A. Schmitt. "Determination of total hardness in water employing visual and spectrophotometric titration procedures." Analytical Chemistry 41.14 (1969): 1954-1958. Yappert, M. Cecilia, and Donald B. DuPre. "Complexometric titrations: competition of complexing agents in the determination of water hardness with EDTA." Journal of Chemical Education 74.12 (1997): 1422.

APPENDICES...