24 Questions
What is the primary purpose of screening in water purification?
To remove floating matter
What is the normality of SHW in terms of CaCO3?
15mg CaCO3
What is the purpose of sedimentation tanks in water purification?
To allow suspended particles to settle down
What is the volume of EDTA required to titrate 20 ml of SHW?
25 ml EDTA
What is the total hardness of the test hard water in ppm?
2160 ppm
What is the reason for adding coagulants in sedimentation?
To produce insoluble, gelatinous, floculant precipitates
What is the permanent hardness of the test hard water in ppm?
1440 ppm
What is the purpose of the middle layer in a sand filter?
To retain coarse particles
What is the temporary hardness of the test hard water in ppm?
720 ppm
What happens to the filter bed over time in filtration?
It becomes less efficient
How is the standard hard water prepared?
By dissolving 1g CaCO3 in dil. HCl and then making up to 1 litre with distilled water
What is the purpose of scraping off the top sand layer in filtration?
To replace it with clean sand
What is the volume of EDTA solution required to titrate 50 ml of the standard hard water?
48 ml EDTA
What is the term used to describe the removal of microorganisms from water?
Disinfection
What are the chemicals used to remove microorganisms from water called?
Disinfectants
What is the purpose of boiling and filtering the test hard water?
To remove temporary hardness
What is the purpose of adding EBT indicator to the Boiled Hard Water (BHW) sample?
To indicate the endpoint of the EDTA titration
What is the normality of the Boiled Hard Water (BHW) sample if 50 ml of BHW requires 20 ml of EDTA solution?
0.2 N
What is the classification of water hardness that is caused by the presence of calcium and magnesium ions?
Permanent hardness
What is the calculation to determine the temporary hardness of a water sample?
Total hardness - Permanent hardness
What is the advantage of using the EDTA titration method for determining water hardness?
It is more accurate and convenient
What is the unit of measurement for water hardness?
ppm
How is the Boiled Hard Water (BHW) sample prepared for EDTA titration?
By adding 10 ml of buffer solution and 3-4 drops of EBT indicator
What is the calculation to determine the hardness of a 0.1M CaCl2 solution?
Molarity x 2 x Eqnt.Wt.CaCO3 x 1000
Study Notes
Methods of Water Purification
- Removal of suspended impurities:
- Screening: water is passed through bar screens with many holes to remove floating matter
- Sedimentation: water is taken to big tanks for 2-6 hours, allowing suspended particles to settle down by gravity
- Sedimentation with coagulation: adds coagulants like alums, FeSO4, NaAlO2 to remove fine clay particles and colloidal matter
- Filtration: water is passed through a bed of fine sand and granular materials to remove colloidal matter, bacteria, and microorganisms
Removal of Microorganisms (Disinfection Methods)
- Disinfection: removing bacteria and microorganisms from water using disinfectants
- Chemicals used: precipitates are filtered off, and the filtrate is collected
EDTA Process
- Used to determine water hardness
- Advantages: more accurate, convenient, and rapid procedure
- EDTA process involves titrating boiled hard water with standardized EDTA till the wine red color changes to blue
Calculating Hardness
- Hardness = Normality x Equivalent Weight of CaCO3 x 1000
- Examples: calculating hardness of 0.1M CaCl2 solution and 0.4 N Ca2+ solution
Determining Hardness of Water
- Steps: preparation of standard hard water, standardization of EDTA, estimation of total hardness, determination of permanent hardness, and determination of temporary hardness
- Examples: calculating total, permanent, and temporary hardness of water samples
Learn about the methods used to purify drinking water, including removal of suspended impurities through screening and sedimentation.
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