Need Help With This Assignment?

Let Our Team of Professional Writers Write a PLAGIARISM-FREE Paper for You!

SUBMIT YOUR ASSIGNMENT

Chemistry

Gravimetric Analysis of Calcium and Hard Water

Gravimetric Analysis of Calcium and Hard Water

Objectives:

I am applying Gravimetric Analysis to test the amount of water hardness in the form of Calcium Carbonate (CaCO3) in samples.

Introduction/Overview/Background:

Water from natural sources may contain various dissolved substances that may reduce its efficacy in its purposes. Due to the challenges that hard water poses to water distribution systems, it is imperative to investigate the level of water hardness to establish the appropriate measures to soften water. Water hardness may vary depending on the route the water goes through and the sources. As water travels over the land surface, it dissolves minerals. Thus, water hardness is the level of mineral content in water. The minerals can be separated into respective cations and anions. Cations may include Na+, Ca2+, Mg2+, and Fe3+, while anions may include NO3 and Cl–. Although these elements may contribute to hardness, we measure water hardness in terms of units of CaCO3 in mg in one liter of water (mg/L). The current experiment employs gravimetric analysis to isolate CaCO3 from water samples and determine water hardness.

Materials used:

  • Digital Scale
  • Clay Triangle
  • Ring Stand
  • Measuring pipet
  • Calcium Chloride
  • Sodium Carbonate Solution
  • Hard water Sample
  • 200ml Beaker
  • 150ml Beaker
  • Distilled water in a Wash bottle
  • Filter Paper
  • Stirring rod
  • Funnel
  • Watch glass

Procedure:

  1. Measure 20.0mL of hard water sample using a pipet
  2. Add 30.0 mL 0.5 M Na2CO3 into a 150 mL beaker.
  • Stir the Solution using a stirring rod.
  1. Leave the Solution to settle for 5 minutes.
  2. Write the initials of the group on the edge of a filter paper.
  3. Fold the filter paper in quarters and tear off a corner of the filter paper.
  • Measure the mass of the filter paper using a digital scale.
  • Place the funnel in the ring stand. Place a 200 mL beaker underneath the funnel.
  1. Place the filter paper in the funnel and use distilled water to moisten the filter paper.
  2. Scrape all of the Solution out of the beaker using a stirring rod and into the filter paper to filter the calcium carbonate precipitate.
  3. Once it is almost completely filtered, rinse the calcium carbonate precipitate three times with distilled water and let it filter completely.
  • After filtration is complete, place the filter paper on a watch glass and dry the precipitate and filter paper in the oven.
  • After drying is complete, measure the mass of both the calcium carbonate precipitate and filter paper using a digital scale.

Experimental Precautions

Sodium Carbonate has an irritating effect on body tissues. Anhydrous calcium chloride is moderately toxic on ingestion and is endothermic when dissolved in water. To avoid eye contact with the chemicals, it is recommended to use goggles/safety glasses during the experiment. A chemical-resistant apron and gloves are also crucial during the investigation. It is important to wash hands thoroughly with soap before leaving the lab.

Results and Discussion

The experiment entailed preparing Na2CO3 and CaCl2 Solution. The balanced equation (i) shows the amount of sediment that will be formed. The calculations for each sample using the formulae provided are recorded as follows;

Sample [CaCl2], M Moles of Ca2+ in 20mL of Solution (mol) Theoretical Amount of CaCO3 Precipitate (g) Volume of 0.5M Na2CO3 (mL) (20% Excess) Theoretical Water Hardness, (mg/L)
1. 0.400 0.008 0.801g 19.2 400
2. 0.200 0.004 0.4004 9.60 200
3. 0.500 0.01 1.0001 24.0 501
4. 0.100 0.002 0.2002 4.80 100
5. 0.050 0.001 0.1001 2.40 50
6. 0.300 0.006 0.60054 14.4 300

 

The number of moles of Ca+ in 20mL and the theoretical amounts per the corresponding CaCl2 samples are as obtained above. Six water samples were used, and the results of the calculations were recorded. Calcium carbonate was added in excess to ensure that all the calcium ions were converted into a product. The volume of the number of Na2CO3 needed to react with CaCl2 completely is shown below.

Precipitate reaction forming Calcium Carbonate

Sample Mass, g Moles & Limiting Reactants Molarity, M CaCO3 Mass, g. Theor. yield CaCO3 Mass, g. Actual yield % yield
CaCl2 2 0.018 0.9 1.8 1.666 92.6%
Na2CO3 2.5 0.0236 1.18

 

The percentage yield of calcium carbonate was calculated to determine the experimental water hardness. The equation of the reaction that produces the mass of CaCO3 used to calculate water hardness is given as follows;

CaCl2 (aq) + Na2CO3 (aq) → 2NaCl(aq) + CaCO3 (s) ………………………………..(i)

Theoretical mass (g) = Molarity (M) × Volume

To obtain the water hardness for each sample, we calculate the concentration of Ca+ in water as follows;

Moles per L x L= Ca+ moles

Then,

For Sample 1 Hardness = (0.801g CaCO3 / 0.020L) x (1000 mg/g) x (1/100) = 400 mg CaCO3/L

The hardness values in mg/L are recorded in the last column of Table 2.

Conclusions

The experiment aimed to apply gravimetric analysis to test the level of water hardness in the form of calcium carbonate CaCO3 using six samples of hard water. To determine the level of hardness, a solution was made by mixing the hard water sample with Sodium Carbonate. Calcium carbonate precipitate was formed, then filtered, rinsed, and dried. The mass of the dry calcium carbonate precipitate was obtained for each sample and used to calculate the hardness. Sample 3 was found to be the hardest water sample with 501mg/L, which can be classified as being very hard. The least hard sample was sample 4, with 50mg/L, which is moderately hard. The method was consistent and valid in determining the hardness for each piece since the average percentage yields for each example were, on average, above 90%, which implied that the maximum number of ions was filtered through. The variation between the actual product and the theoretical work was small.

Reference

Lab Manual: Gravimetric Analysis of Calcium and Hard Water as well as Silver Recovery

ORDER A PLAGIARISM-FREE PAPER HERE

We’ll write everything from scratch

Question 

Objectives:

Gravimetric Analysis of Calcium and Hard Water

Gravimetric Analysis of Calcium and Hard Water

Write the main aim of this investigation.

Introduction/Overview/Background:

Apart from the lab manual, students are required to do more research on the topic related to the investigation and write the introduction part. If possible, you may also collect appropriate pictures and show them in this section.

Materials used:

It’s very important to record all materials used in the lab because the lab report must show what materials have been used in the experiment.

Procedure:

You may write the procedure in your sentences based on your handle in the lab. If possible, you may also show some pictures dealing with the experiment.

Results and Discussion:

Show your results in the form of tables or plots (e.g., linear, exponential, or other correlation plots) and discuss your results for each section of the investigation.

If molecular compounds are involved in the lab, you must draw all molecules by hand before you turn in the report, and such practice will be useful for the drawing skills of any molecular structures.

Here, you must show the % error when you compare the experimental data with the actual value.

Conclusions:

Summarize your results and conclude them with appropriate reasonings, including accuracy, preciseness, and errors.