30 Questions
Define pH and how is it calculated?
pH is a measure of the acidic or alkaline condition of water and is calculated as pH = -log {H+}.
What is the equilibrium constant for water at 25°C?
The equilibrium constant for water at 25°C is Kw = 10^-14.
Explain why the pH of deionized water at 25°C is 7.0.
The pH of deionized water is 7.0 at 25°C because the concentration of hydrogen ion and hydroxyl ion is both 10^-7 M.
What does a pH value of less than 7 indicate?
A pH value of less than 7 indicates acidity.
Explain why groundwater is often slightly acidic.
Groundwater is often slightly acidic due to the presence of excess carbon dioxide.
How is the activity of water treated in the equation Kw = {H+}{OH-}?
The activity of water is considered as a constant and its activity is taken as 1.0 in the equation Kw = {H+}{OH-}.
What materials are required for measuring the pH of a sample?
pH meter, 200 mL beaker, wash bottle, tissue paper
Why is it important to keep samples at 4°C before analyzing pH?
To reduce changes in the sample and maintain its integrity.
How does temperature affect the measurement of pH?
Temperature can change the electrode output and the inherent pH of the sample.
Why is preservation of the sample not practical?
Biological activity continues, leading to changes in the sample.
What precautions should be taken while performing the pH experiment?
Noting pH and temperature, using temperature compensation or calibration.
What role do buffer solutions play in the pH determination process?
Buffers are used to calibrate the pH meter since their pH values are known.
What can cause the measured turbidity values to be low?
The presence of coloured solutes
What can cause the measured turbidity values to be high?
Precipitation of dissolved constituents (e.g., Fe)
How can light absorbing materials affect turbidity readings?
Light absorbing materials can cause low readings
What can give low readings in turbidity measurement if present in the water?
Floating debris and coarse sediments
What can cause high readings in turbidity measurement?
Finely divided air bubbles
What should be done if turbidities exceed 40 units?
Dilute the sample with turbidity-free water
Why is it advised to record pH along with color when testing water?
To monitor the quality of water and assess any potential issues.
What is the environmental significance of color in water?
Presence of color in water, usually from natural organics, can lead to the formation of harmful byproducts during disinfection.
Why is it important to limit the color of water for domestic supplies?
To prevent the formation of harmful disinfection byproducts like tri-halomethanes.
What is the drinking water guideline value for color according to Bangladesh Environment Conservation Rules (1997)?
15 Pt-Co Unit
How is the standard color solution method used to determine the color of water?
By comparing the color produced by 1 mg/l of platinum and 0.5mg/l of cobalt to the standard color solution.
What type of appearance do waters containing natural color typically have?
Yellow-brownish
Explain how the turbidity of the original sample is calculated if 5 volumes of turbidity-free water were added to 1 volume of sample, and the diluted sample showed a turbidity of 30 units.
The turbidity of the original sample is calculated by multiplying the turbidity of the diluted sample by the dilution factor, which in this case is 6 (5 volumes of water + 1 volume of sample). Therefore, 30 NTU x 6 = 180 NTU.
Why is turbidity important in filtration processes?
Turbidity is important in filtration processes because high turbidity levels can clog filters quickly and reduce their efficiency, leading to the need for more frequent filter replacements.
Why is turbidity important in disinfection processes?
Turbidity is important in disinfection processes because particles in turbid water can shield harmful microorganisms from disinfectants, reducing the effectiveness of the disinfection process.
What are some commonly used methods for removing turbidity from water?
Common methods for removing turbidity from water include sedimentation, coagulation, flocculation, and filtration.
Discuss the nature of materials that cause turbidity in polluted river water.
Materials that cause turbidity in polluted river water include suspended particles like silt, clay, organic matter, and microorganisms.
What limit is typically placed on turbidity in water supplies by current standards and why is such a limit set?
The typical limit placed on turbidity in water supplies is 1 NTU. This limit is set to ensure that water is visually clear and to prevent interference with disinfection processes.
Learn how to determine the pH level of water, which indicates its acidic or alkaline nature. Understand the concept of pH as a measure of hydrogen ion concentration in water and the dissociation of water molecules into hydrogen and hydroxyl ions.
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