lab report experiment 5 chm421

High School
You don't have any recent items yet.
You don't have any courses yet.
You don't have any books yet.
You don't have any Studylists yet.
Information

CHM421 - Experiment 5: Distillation and Hardness of Water

Analytical chemistry (chm421), mara university of technology (shah alam), recommended for you, students also viewed.

LAB Report Experiment 1 CHM421
Neutralisation Capacity Of Commercial Antacid Tablet
Distillation and Hardness of Water
Determination of Fe in a Ferum Solution By Gravimetric Analysis
Separation of Amino Acid

Related Studylists

Preview text.

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, you 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 other water samples to determine the effectiveness of the distillation procedure. Today's experiment will make use of one of the four types of volumetric method of analysis, ie the complexation titration to determine the hardness of water sample.

You may have heard of the terms 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 amounts of calcium and magnesium salts present in the water. Since soap consists of fatty acid salts (e., sodium stearate) and the fatty acid salts of calcium and magnesium are insoluble in water (scum), the effectiveness of 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 precipitate form, hard water will cause a layer of calcium carbonate on the heating coil of a kettle and thus will require more time to boil water. In this experiment, we use the method of 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 requires the input of energy to convert a liquid to its vapour and then condensation of the vapour to liquid in another part of the distillation apparatus. Impurities with low boiling point will vaporise and condense first and can be collected and put aside. High boiling impurities on the other hand will remain in the distilling flask unless more heat is provided. Boiling will occur when the vapour pressure of a substance equals the confining pressure. When the confining pressure is atmospheric pressure we call the temperature at which boiling occurs the normal boiling point. There are many parameters that contribute to the efficiency of separation. These include the length and packing of the distilling column, the distillation rate, and the confining pressure. What you will 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 by 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 are used, hydrogen and hydroxide ions are produced which then react with each other to yield water. Water purified by this method is called deionised 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 water by titrating the sample with a standard solution of ethylenediamine-tetraacetic acid (EDTA). Hardness is more commonly expressed in unit of ppm rather than molarity because of the low concentration value.

25 mL 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 into the lab notebook.

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 solution was in a pale pink colour. The drops of the indicator were not added too many since it can create problems with seeing the end point. Titrate the sample with the EDTA solution immediately against a white background until the light pink solution turns to light sky blue. The volume of the burette at the end point was recorded. The recorded data was double checked to make sure the correct reading was recorded into the notebook. The whole process was recorded with at least two more samples.

Water Hardness

The water hardness was determined by titration on lab tap water, lab distilled water, deionised water, home tap water, distilled home tap water and 0 M NaCl.

The burette was filled up with more EDTA solution following the above titration.

A 25 mL pipette was rinsed with tap water and 25 mL of lab tap water was pipette into a 250 mL conical flask. The content of the pipette was emptied into the flask and the last drop was touched onto the interior wall of flask. The remaining liquid in the pipette tip was not blown into the flask as it will give more than 25 mL liquid.

Similarly, 8 mL of the ammonia-ammonium chloride buffer and 3 drops of Eriochrome Black T were added as above into the water sample in the flask. The initial burette was read and recorded to the nearest 0 mL. The standard EDTA solution was carefully added in the burette to the water sample in the flask. The addition of titrant was slow down as the formation of blue colour in the solution started to be seen to drop wise addition. The red colour of solution will be replaced by a blue colour when all the calcium and magnesium in the sample had been exhausted. The titration was stopped at the first colour changed that was observed, the final burette reading was read and recorded. The titration was repeated with another two more labs tap water samples.

A little bit of lab distilled water was obtained using the rubber filler. The filler was removed, the pipette was tilted and rotated to rinse the inside of the pipette with distilled water. The tainted distilled water was thrown away. 25 mL of fresh distilled water was pipette into a cleaned but the flask was not necessarily dried. The buffer and indicator were added as above and the standardized EDTA solution was titrate. The steps were repeated.

The pipette was rinse with home tap water or ammonia-ammonium or an unknown supplied by the instructor. 25 mL of the unknown was pipette into a clean flask. Buffer and indicator were added with the standardized EDTA solution. The method was repeated for the rest of the samples above and the data was recorded into the notebook.

Calculation

The objectives were achieved. The water sample was purified by distillation. The EDTA solution was also standardize. Lastly, the hardness of water sample was also analysed by titration with EDTA. The hardness of six water sample which are lab tap water, lab distilled water, home tap water, distilled home tap water, deionized water and 0 M of NaOH are 146 ppm, 146 ppm, 12 ppm, 1 ppm, 44 ppm and 6 ppm respectively. Each six water samples have the total amount of calcium and magnesium ion of 0 mol/L, 0. mol/L, 116 mol/L, 960 mol/L, 33 mol/L and 225 mol/L respectively.

Question(s)

Why should the water in the condenser flow uphill during distillation?

This is because 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 to come out of the system as a vapour.

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 between lab tap water and lab distilled water is the same meanwhile the hardness of home tap water is higher than home distilled water.

The distillation did have a significant effect on the water hardness since it removes all the impurities of home tap water. It is pure and does not contain any impurities.

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 analysed in the experiment.

Home tap water, distilled home tap water, deionized water and 0 M of NaOH are classified as soft since it has a range of ppm below 60 ppm.

Lab tap water and lab distilled water both are classified as hard since it have 140 ppm which is in between the range for hard (120-180 ppm).

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

As the conductance increase, the hardness also increase.

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.

Casiday, R., & Frey, R. (n.). Water Hardness. Water hardness. Retrieved January 8, 2022, from chemistry.wustl/~edudev/LabTutorials/Water/FreshWater/hardness

Testing the hardness of water. RSC Education. (2015, July 7). Retrieved January 8, 2022, from edu.rsc/experiments/testing-the-hardness-of-water/426.article

Multiple Choice

Course : Analytical Chemistry (CHM421)

University : mara university of technology (shah alam).

Discover more from: Analytical Chemistry CHM421 MARA University of Technology (Shah Alam) 94 Documents Go to course
More from: Analytical Chemistry CHM421 MARA University of Technology (Shah Alam) 94 Documents Go to course
More from: CHM421 by evelyn xavier 17 17 documents Go to Studylist