EXP 5 CHM 421 - LAB REPORT PDF

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ANALYTICAL CHEMISTRY (CHM421)EXPERIMENT 5:DISTILLATION AND HARDNESS OFWATERNAME: MAIZURAH BINTI RAMLIMATRIX NUMBER: 2020605174GROUP: AS2532APREPARED FOR: DR. MOHD AZRI AB RANIDATE OF EXPERIMENT: 19/04/DATE OF SUBMISSION: 26/04/ABSTRACT:This experiment aimed to purify the water sample by distillation...

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ANALYTICAL CHEMISTRY (CHM421) EXPERIMENT 5:

DISTILLATION AND HARDNESS OF WATER NAME: MAIZURAH BINTI RAMLI MATRIX NUMBER: 2020605174 GROUP: AS2532A1 PREPARED FOR: DR. MOHD AZRI AB RANI DATE OF EXPERIMENT: 19/04/2021 DATE OF SUBMISSION: 26/04/2021

ABSTRACT: This experiment aimed to purify the water sample by distillation, standardize the EDTA solution, and analyze the water sample's hardness by titration with EDTA solution. Firstly, the water sample was distillate until enough distillate produced. The temperature at the start of collecting the distillate is 96.0 °C. The temperature at the end of collecting the distillate is 99.0 °C. After that, the concentration of EDTA solution was obtained through standardization of EDTA solution against Ca 2+ solution, which is

4.94 × 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. This data will be used to calculate the hardness of the water in terms of ppm unit. The hardness of Lab Tap Water (37.54 ppm), Lab Distilled Water (37.54 ppm), Home Tap Water (32.63 ppm), Distilled Home Tap Water (37.58 ppm), 0.1 M NaCl (16.82 ppm) and Deionized Water (115.12 ppm). OBJECTIVES: 1. To purify water sample by distillation. 2. To standardize EDTA solution. 3. To analyses the hardness of the water sample by titration with EDTA. INTRODUCTION: Distillation is probably the most common method used in the purification of liquids and can separate components of a mixture if they have a different boiling point. This process involves converting a liquid into a vapour that is eventually condensed back to liquid form. Impurities with a low boiling point will vaporize and condense first and can be collected and put aside. Impurities with a high boiling point will remain in the distilling flask except if more heat is provided. When the vapour pressure of a substance equals the confining pressure, which is atmospheric pressure, the boiling temperature is the standard boiling point. The length and packing of the distilling column, the distillation rate, and the confining pressure contribute to separation efficiency. This experiment is carried out to purify home tap water and then compare the hardness of the original tap water with the distilled water and other samples to determine the effectiveness of the distillation procedure.

Hard water is the water that presence of large ions like calcium and magnesium. So, water hardness can be defined as measuring the total amounts of calcium and magnesium salts dissolved in water and usually expressed in a ppm unit rather than molarity because of the low concentration value. Effects of hard water can be seen when we used more soap or detergent to do the cleaning job. The effectiveness of soap will decrease as hardness increases due to precipitation with magnesium and calcium. In this experiment, we will be using complexometric titration to determine the hardness of the water sample. The water sample will go through titration with a standard solution of ethylenediamine-tetraacetic acid (EDTA). Other methods can soften hard water, such as replacing the calcium and magnesium ions in the water sample with other ions. For example, home water usually replaces calcium and magnesium with sodium ions. Deionized water also can be obtained through an electrically charged resin. These will then exchange the positively charged ions (cations) and negatively charged ions (anions) for hydrogen and hydroxyl ions if both hydrogen and hydroxide ions are produced, which then react with each other to yield water called deionized water. This method is commonly used to purify water for chemistry labs. METHOD:

As illustrated in the picture above, 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. 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 were pipette and transferred to a 250mL conical flask. The concentration of the CaCO3 prepared was recorded. Next, 8mL 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. 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 25.0mL of lab tap water was pipette into a 250 mL conical flask. 8mL 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 0.01mL. 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 colour 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. DATA AND 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 = 0.007M Volume of the standard Ca2+ solution = 25.0 ml Final reading of EDTA solution (mL) Initial reading of EDTA solution (mL) Volume of EDTA solution (mL)

Rough 37.50

1 35.75

2 35.55

0.10

0.15

0.20

37.40

35.60

35.35

C. Hardness of Water Concentration of EDTA =

4.94 × 10−3 M Deionized water

0.1 M NaCl

1.85

Distilled home tap water 0.30

9.90

10.85

2.10

0.20

0.10

4.10

10.00

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) Hardness (ppm)

3.75 × 10-4

3.75 × 10-4

3.26 × 10-4

3.95 × 10-5

1.15×10-3

1.68×10-4

37.54

37.54

32.63

37.58

115.12

16.82

Home tap water

2.00

Lab distilled water 4.00

0.10

Water sample

Lab tap water

Final reading of standard EDTA (mL) Initial reading of standard EDTA (mL) Volume of standard EDTA used (ml)

CALCULATION:

B. Standardization of the EDTA solution ROUGH M 1 V 2= M 2 V 2 M 1(37.40 mL)=( 0.007 M )( 25.0 mL ) −3

M 1=4.68 ×10 M

TRIAL 1 M 1 V 1=M 2 V 2 (0.007 M )(25.0 mL )=M 2 (35.6 mL ) M 2=4.92 ×10−3 M

TRIAL 2 M 1 V 1=M 2 V 2 (0.007 M )( 25.0 mL )= M 2 (35.35 mL ) M 2=4.95 ×10−3 M

Average of Molarity of EDTA =

4.92 × 10−3 M + 4.95 ×10−3 M 2 −3

¿ 4.94 × 10 M

C. Hardness of Water LAB TAP WATER

LAB DISTILLED WATER

Molarity of [Ca2+ + Mg2+]

Molarity of [Ca2+ + Mg2+]

M 1 V 2=M 2 V 2 −3 M 1(25.0 mL)=( 4.94 ×10 M )( 1.90 mL) M 1=3.75 ×10−4 M Hardness = ppm = mg/L −4

3.75 ×10

mol 100.1 g CaC O 3 1000 mg × × 1g 1 mol CaC O3 L

M 1 V 2= M 2 V 2 −3 M 1(25.0 mL)=( 4.94 ×10 M )( 1.90 mL ) M 1=3.75 ×10−4 M Hardness = ppm = mg/L −4

3.75 ×10

mol 100.1 g CaC O 3 1000 mg × × 1g 1 mol CaC O3 L

= 37.54 ppm

= 37.54 ppm

HOME TAP WATER

DISTILLED HOME TAP WATER

Molarity of [Ca2+ + Mg2+]

Molarity of [Ca2+ + Mg2+] M 1 V 2=M 2 V 2 −3 M 1(25.0 mL)=( 4.94 ×10 M )( 1.65 mL ) M 1=3.26 ×10−4 M Hardness = ppm = mg/L 3.26 ×10

−4

M 1 V 2= M 2 V 2 −3 M 1(25.0 mL)=( 4.94 ×10 M )( 1.90 mL ) M 1=3.75 ×10−4 M Hardness = ppm = mg/L

mol 100.1 g CaC O 3 1000 mg × × 1g 1 mol CaC O 3 L

−4

3.75 ×10

mol 100.1 g CaC O 3 1000 mg × × 1g 1 mol CaC O3 L

= 32.63 ppm

= 37.58 ppm

DEIONIZED WATER

0.1M NaCl

Molarity of [Ca2+ + Mg2+]

Molarity of [Ca2+ + Mg2+]

M 1 V 2=M 2 V 2 −3

M 1(25.0 mL)=( 4.94 ×10 M )( 5.80 mL) M 1=1.15 ×10−3 M

Hardness = ppm = mg/L mol 100.1 g CaC O 3 1000 mg × × L 1 mol CaC O 3 1g = 115.12 ppm −3

1.15 × 10

M 1 V 2= M 2 V 2 −3

M 1(25.0 mL)=( 4.94 ×10 M )( 0.85 mL ) M 1=1.68 ×10−4 M

Hardness = ppm = mg/L −4

1.68 ×10

= 16.82 ppm

mol 100.1 g CaC O 3 1000 mg × × L 1 mol CaC O3 1g

DISCUSSION: The results from this experiment were not very reasonable. In the second part of this experiment, I obtained the average molarity of EDTA solution, which is

−3 4.94 × 10 M . Using

the molarity result and the volume of EDTA solution used in part C, the concentration of Ca 2+ + Mg2+ can be calculated. Then I can determine the hardness of each water that usually expressed in ppm CaCO3. Hardness defined as the measurement of the total amounts of calcium and magnesium salts present in water. If water has a large amount of calcium and magnesium ion in it, the hardness will be enormous. As I calculate all the result, then I got the hardness of Lab Tap Water (37.54 ppm), Lab Distilled Water (37.54 ppm), Home Tap Water (32.63 ppm), Distilled Home Tap Water (37.58 ppm) and 0.1 M NaCl (16.82 ppm) and Deionized Water (115.12 ppm). Supposedly, the deionized water has a low hardness since it has low ion dissolved in water. The hardness of water can be categorized based on each range 0-60 ppm is termed soft, 60-120 ppm is medium-hard, 120-180 ppm is hard, and above 180 ppm is very hard. All water samples have termed soft hardness, except deionized water has medium-hard hardness. When listing the samples' hardness in increasing order, 0.1 M NaCl < home tap water < lab water and lab distilled water < distilled home tap water < deionized water. Deionized water is the hardest, and 0.1M NaCl is the softest. The results showed that some errors might occur, affecting the accuracy of the result in this experiment. The possible error that can occur is during doing the titration, which is the inaccuracy endpoint. The endpoint had already been passed, resulting in the volume of titrant delivered is too large. This error can be solved by doing a rough titration to determine the approximate endpoint and observing the colour change. During the second titration, add the EDTA to with 1mL of the endpoint of the rough titration, then titrate dropwise and very slowly with swirling to the red to blue colour change endpoint. The standardization EDTA titration should be done at least two titrations to reduce the per cent error. Other than that, the parallax error while taking a reading from the apparatus such as burette. By ensuring your eyes are perpendicular to the scale of an apparatus, we can get better titration. Finally, the calcium standard is not homogenous, resulting in the molarity of EDTA will probably in error. So the calcium standard must be homogenous before using it during the standardization of EDTA.

CONCLUSION: In conclusion, the water sample was purified by distillation. The initial and final temperature of the collected distillate were 96℃ and 99℃ , respectively. The experimental boiling range for the collected sample is 97.5°C. −3

The concentration of ETDA is

which can be obtained through the standardization of ETDA solution. Lastly,

4.94 × 10 M

we can know the hardness of Lab Tap Water (37.54 ppm), Lab Distilled Water (37.54 ppm), Home Tap Water (32.63 ppm), Distilled Home Tap Water (37.58 ppm) and 0.1 M NaCl (16.82 ppm) are categories as termed soft that have a range between 0 to 60 ppm. Deionized water was categorized as medium-hard water because it has 115.12 ppm. REFERENCES: 5.2:

Simple

Distillation.

(2017,

November

20).

Chemistry

LibreTexts.

https://chem.libretexts.org/Bookshelves/Organic_Chemistry/Book %3A_Organic_Chemistry_Lab_Techniques_(Nichols)/05%3A_Distillation/5.02%3A_Si mple_Distillation EDTA

ERROR

ANALYSIS.

(n.d.).

Genchem.rutgers.edu.

http://genchem.rutgers.edu/EDTAerr.html Hardness,Conductivity,TDS

measurement.

(2011).

Globalw.com.

http://www.globalw.com/support/hardness.html in.

(2014,

June

25).

Water

flow

in

condenser.

Chemistry

Stack

Exchange.

https://chemistry.stackexchange.com/questions/13911/water-flow-in-condenser Madsen, A. A. (2020, June 3). How to make deionized water . Earth and Human. https://earthandhuman.org/how-to-make-deionized-water/

QUESTIONS: 1. Why should the water in the condenser flow uphill during distillation? It was to force the cold water to fill in the condenser completely. So the condenser does not heat the inner surface that can cause the distilled material will come out of the system as vapour.

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 hardness of lab water is the same as the lab distilled water, while the hardness of home tap water is higher than the distilled water. Yes, distillation can affect the water hardness by removing all the impurities. So all the distilled water are pure and does not contain impurities.

3. Water with hardness in the range 0-60 ppm is termed soft, 60-120 ppm is medium-hard, 120-180 ppm is hard, and above 180 ppm is very hard. Classify the water samples that you analyzed in the experiment. Termed Soft

Medium-hard

Hard

Very Hard

(0-60 ppm) Lab Tap Water

(60-120) Deionized Water

(120-180) -

(180-above) -

Lab Distilled Water Home Tap Water Distilled Home Tap Water 0.1 M NaCl

4. Do you think there should be a correlation between conductance and hardness results? Explain your answer. As the conductance increase, the hardness also will increase. Conductivity increases with

increasing ion content, while hardness also increases when the amount of calcium and magnesium ion increases. 5. Suggest any ways you can think of to improve any parts of this experiment. The experiment should be repeated at least once to ensure that the value of the titre that was obtained was accurate. We need to be careful in the titration step as we may slightly beyond the endpoint resulting in the volume of titrant delivered is too large. It is important to perform a rough titration to determine the approximate endpoint and to observe colour change. When carrying out the following titrations after the rough one, add very rapidly within about 2 or 3 mL of the endpoint and then titrate very carefully, drop by drop at a time to the endpoint....