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In this experiment, it is assumed that No. of moles of (Ca2+ + Mg2+) = moles (Ca2+).   Calculate the number of moles of Ca2+ in the hard water sample. please show working out, thank you    Sample No. 1 2 3 4 Final Burette reading (mL)   24.40 46.90 24.70 47.20 Initial Burette reading (mL) 0.10 24.40 2.10 24.70 Final-Initial Titre (mL) 24.30 22.50 22.60 22.50

In this experiment, it is assumed that No. of moles of (Ca2+ + Mg2+) = moles (Ca2+).   Calculate the number of moles of Ca2+ in the hard water sample. please show working out, thank you    Sample No. 1 2 3 4 Final Burette reading (mL)   24.40 46.90 24.70 47.20 Initial Burette reading (mL) 0.10 24.40 2.10 24.70 Final-Initial Titre (mL) 24.30 22.50 22.60 22.50

Chemistry
Chemistry
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ISBN:9781305957404
Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Publisher:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Chapter1: Chemical Foundations
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In this experiment, it is assumed that No. of moles of (Ca2+ + Mg2+) = moles (Ca2+).   Calculate the number of moles of Ca2+ in the hard water sample. please show working out, thank you   

Sample No.

1

2

3

4

Final Burette reading

(mL)

 

24.40

46.90

24.70

47.20

Initial Burette reading

(mL)

0.10

24.40

2.10

24.70

Final-Initial Titre (mL)

24.30

22.50

22.60

22.50
PROCEDURE: 1. In a weighing bottle, weigh out accurately on the analytical balance 0.9 - 1.1 g of the zinc metal provided. 2. Transfer the metal carefully to a 50 ml conical flask and in the fume hood, carefully add ~4 ml of concentrated HCl into the flask to dissolve the metal 3. Cool the solution and add concentrated NaOH drop-wise until a permanent faint white precipitate forms. 4. Add 5 M HCl drop-wise to neutralize the solution until the zinc hydroxide (Zn(OH)2) precipitate just dissolves. Add a further 5 drops more of the acid to acidify the solution. Transfer the solution carefully to a 250 ml volumetric flask and make up to the mark with distilled water. Stopper the flask firmly and shake it to ensure a homogeneous solution. Using a buretta deliver exactly 20.00 ml of the standard zinc solution into a clean 5. 6. 250 ml conical flask. Add 70 ml of distilled water and 10 ml of the buffer solution (pH = 10). Then add four (4) drops of the indicator solution 7. Repeat step (6) a further 3 times so that you have a total of four conical flasks of solution for consecutive titrations. 8. Titrate with the EDTA solution until the end-point is reached (WINE-RED to PURE BLUE). 9. Repeat the titration until three (3) concordant results are obtained.
Transcribed Image Text:PROCEDURE: 1. In a weighing bottle, weigh out accurately on the analytical balance 0.9 - 1.1 g of the zinc metal provided. 2. Transfer the metal carefully to a 50 ml conical flask and in the fume hood, carefully add ~4 ml of concentrated HCl into the flask to dissolve the metal 3. Cool the solution and add concentrated NaOH drop-wise until a permanent faint white precipitate forms. 4. Add 5 M HCl drop-wise to neutralize the solution until the zinc hydroxide (Zn(OH)2) precipitate just dissolves. Add a further 5 drops more of the acid to acidify the solution. Transfer the solution carefully to a 250 ml volumetric flask and make up to the mark with distilled water. Stopper the flask firmly and shake it to ensure a homogeneous solution. Using a buretta deliver exactly 20.00 ml of the standard zinc solution into a clean 5. 6. 250 ml conical flask. Add 70 ml of distilled water and 10 ml of the buffer solution (pH = 10). Then add four (4) drops of the indicator solution 7. Repeat step (6) a further 3 times so that you have a total of four conical flasks of solution for consecutive titrations. 8. Titrate with the EDTA solution until the end-point is reached (WINE-RED to PURE BLUE). 9. Repeat the titration until three (3) concordant results are obtained.
Classification Soft Moderately Hard Hard Very Hard mg/L or ppm 6. 7. 8. 0-60 61-120 121-180 > 180 PROCEDURE: 1. Dilute the EDTA solution by dispensing 25.0 ml of the given EDTA from a burette into a 250 ml volumetric flask and make up to the mark with distilled water. 2. Rinse and fill the burette with the diluted EDTA solution. 3. Dispense a 20 ml aliquot of the hard water sample into a 250 ml conical flask. Add 2 ml of buffer solution (pH 10). Add 4 drops of the Eriochrome black T indicator solution. 4. Repeat step (3) a further 3 times so that your have four conical flasks of the water solution for the repeat titrations. 5. Titrate the water sample with the EDTA solution until the colour changes from wine-red to pure blue. Repeat the titration until three (3) concordant results are obtained. Express the water hardness in mol L-1 of (Ca²+ + Mg²+). Assuming the water hardness is only due to the presence of Ca²+, express the water hardness in terms of mg L-1 of CaCO3.
Transcribed Image Text:Classification Soft Moderately Hard Hard Very Hard mg/L or ppm 6. 7. 8. 0-60 61-120 121-180 > 180 PROCEDURE: 1. Dilute the EDTA solution by dispensing 25.0 ml of the given EDTA from a burette into a 250 ml volumetric flask and make up to the mark with distilled water. 2. Rinse and fill the burette with the diluted EDTA solution. 3. Dispense a 20 ml aliquot of the hard water sample into a 250 ml conical flask. Add 2 ml of buffer solution (pH 10). Add 4 drops of the Eriochrome black T indicator solution. 4. Repeat step (3) a further 3 times so that your have four conical flasks of the water solution for the repeat titrations. 5. Titrate the water sample with the EDTA solution until the colour changes from wine-red to pure blue. Repeat the titration until three (3) concordant results are obtained. Express the water hardness in mol L-1 of (Ca²+ + Mg²+). Assuming the water hardness is only due to the presence of Ca²+, express the water hardness in terms of mg L-1 of CaCO3.
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