Water Technology: Hardness of Water
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Questions and Answers

What is the main cause of temporary hardness in water?

  • High chloride content
  • Excess dissolved oxygen
  • Dissolved bicarbonates of Ca and Mg (correct)
  • Soluble non-carbonate salts of Ca and Mg

    • Permanent hardness can be removed by boiling.

    False

    What is the formula to express hardness of water in parts per million (ppm)?

    Parts of CaCO3 equivalents per million parts of water.

    Hard water creates _____ when mixed with soap.

    <p>insoluble white scum</p> Signup and view all the answers

    Match the type of hardness with its characteristics:

    <p>Temporary Hardness = Can be removed by boiling Permanent Hardness = Requires special chemical treatments Both types = Total Hardness = Temporary + Permanent Hardness Hard Water = Consumes large amounts of soap</p> Signup and view all the answers

    Which component in water is associated with clogging pipes?

    <p>Hardness</p> Signup and view all the answers

    What are two main types of hardness in water?

    <p>Temporary Hardness and Permanent Hardness</p> Signup and view all the answers

    What is the primary role of AgSO4 in the back titration procedure?

    <p>To oxidize straight chain organic compounds and aromatics</p> Signup and view all the answers

    The presence of Cl- ions does not interfere in the reaction due to the addition of HgSO4.

    <p>True</p> Signup and view all the answers

    What is the total mass of Mohr's salt used to prepare the solution?

    <p>4.0 g</p> Signup and view all the answers

    1 ml of 1N FAS solution is equivalent to ______ mg of oxygen.

    <p>8</p> Signup and view all the answers

    Match the following compounds with their roles in the procedure:

    <p>AgSO4 = Catalyst, oxidizes organic compounds HgSO4 = Prevents interference of Cl- ions Ferroin = Indicator for titration Potassium dichromate = Oxidizing agent in waste water analysis</p> Signup and view all the answers

    What does EDTA react with in order to determine permanent hardness?

    <p>Calcium ions</p> Signup and view all the answers

    Temporary hardness can be calculated by subtracting permanent hardness from total hardness.

    <p>True</p> Signup and view all the answers

    What is the primary purpose of dissolved oxygen in water?

    <p>To support biological oxidation of pollutants.</p> Signup and view all the answers

    The reaction that produces iodine in the determination of dissolved oxygen involves ____ reacting with sodium thiosulfate.

    <p>I2</p> Signup and view all the answers

    Match the following processes with their corresponding reactions:

    <p>Permanent Hardness = EDTA titration Dissolved Oxygen Estimation = Winkler’s Method Alkaline KI reaction = Releases I2 Dissolved Oxygen = Oxidizes KI to I2</p> Signup and view all the answers

    Which chemical is used in Winkler’s Method to liberate iodine for the determination of dissolved oxygen?

    <p>H2SO4</p> Signup and view all the answers

    Oxygen dissolves in water exclusively from photosynthesis.

    <p>False</p> Signup and view all the answers

    What does the 'V2' represent in the calculation of permanent hardness?

    <p>The volume of EDTA consumed.</p> Signup and view all the answers

    Total hardness can be expressed as ____ in ppm.

    <p>mg dm-3</p> Signup and view all the answers

    What is the first step in determining dissolved oxygen using Winkler’s Method?

    <p>Adding MnSO4</p> Signup and view all the answers

    What does 1 ppm of CaCO3 equivalent hardness represent?

    <p>1 part of CaCO3 in 1 million parts of water</p> Signup and view all the answers

    Milligram per litre (Mg/L) represents the number of milligrams of CaCO3 in one litre of water.

    <p>True</p> Signup and view all the answers

    What is the German degree of hardness (dGH) defined as?

    <p>10 mg/L CaO or 17.848 ppm</p> Signup and view all the answers

    During the EDTA titration, the color changes from _____ to _____ when the complex is formed.

    <p>pink, blue</p> Signup and view all the answers

    Match the parameters to their definitions:

    <p>ppm = Parts per million of CaCO3 Mg/L = Milligrams of CaCO3 per litre dGH = German degree of hardness EDTA = Chemical used for titrating hardness</p> Signup and view all the answers

    What is the purpose of adding NH3-NH4Cl buffer in the hardness determination process?

    <p>To maintain appropriate pH for the reaction</p> Signup and view all the answers

    The reaction Ca-EBT complex with EDTA results in a pink color.

    <p>False</p> Signup and view all the answers

    What is the molarity formula for preparing standard EDTA solution?

    <p>Wt of EDTA salt x 4 / Mol wt of EDTA salt</p> Signup and view all the answers

    To determine total hardness, you titrate the water sample against a standard _____ solution.

    <p>EDTA</p> Signup and view all the answers

    What is the formula for calculating the normality of dissolved oxygen (D.O) in water?

    <p>N2 = (N1 x V1) / 100</p> Signup and view all the answers

    Biological Oxygen Demand (B.O.D) measures the amount of oxygen required for the anaerobic oxidation of organic matter.

    <p>False</p> Signup and view all the answers

    What does B.O.D stand for?

    <p>Biological Oxygen Demand</p> Signup and view all the answers

    Dissolved oxygen is capable of oxidizing biologically __________ pollutants.

    <p>oxidizable</p> Signup and view all the answers

    Match the following terms with their definitions:

    <p>Dissolved Oxygen = Oxygen available in water for oxidation Biological Oxygen Demand = Oxygen required for biological oxidation of organic matter MnSO4 = Chemical used to treat water samples for D.O Na2S2O3 = Standard solution used in titration of iodinated solutions</p> Signup and view all the answers

    What happens to Mn2+ in the presence of dissolved oxygen during B.O.D determination?

    <p>Mn2+ is oxidized to Mn4+</p> Signup and view all the answers

    The incubation period for measuring B.O.D is 10 days at 20°C.

    <p>False</p> Signup and view all the answers

    What is the effect of temperature on B.O.D readings?

    <p>Higher temperatures can increase B.O.D readings by promoting microbial activity.</p> Signup and view all the answers

    The volume of water sample taken for B.O.D determination is __________ ml.

    <p>100</p> Signup and view all the answers

    What is the primary reason for diluting sewage water samples during B.O.D testing?

    <p>To ensure accurate D.O readings</p> Signup and view all the answers

    Study Notes

    Water Technology

    • Water is essential for animals and plants, used in domestic and industrial applications
    • Water quality affects health, agriculture, and industry
    • Key components analyzed in water include hardness, nitrate, sulfate, chloride, and dissolved oxygen
    • Hardness in water is a measure of its capacity to precipitate soap
    • Hard water contains soluble salts (Ca, Mg, Fe, Mn) that interfere with soap lathering
    • Hard water forms scales on boiler pipes and damages them
    • Two types of water hardness: temporary and permanent

    Hardness of Water

    • Temporary hardness is caused by calcium and magnesium bicarbonates which can be removed by boiling
    • Permanent hardness is caused by soluble salts such as chlorides, sulfates, and nitrates, which cannot be removed by boiling.
    • Total Hardness = Temporary Hardness + Permanent Hardness

    Units of Hardness

    • Hardness is typically measured in parts per million (ppm) or milligrams per liter (mg/L)
    • Hardness degrees are also used and equal 10 mg/L CaCO3

    Determination of Hardness (EDTA Method)

    • The EDTA method uses Eriochrome Black-T (EBT) indicator to determine hardness concentration
    • Ca²⁺ and Mg²⁺ ions react with EDTA, changing the indicator color
    • Titration with a standard EDTA solution is used to find the concentration of these ions
    • Procedures for this involve preparing standard EDTA solutions, and solutions to determine both temporary and permanent hardness
    • Calculations using volume of EDTA consumed to calculate hardness in ppm.

    Dissolved Oxygen

    • Dissolved oxygen comes from the atmosphere and photosynthesis by aquatic plants
    • Dissolved oxygen is necessary for biodegradation of pollutants
    • Winkler's method is used to determine dissolved oxygen levels
    • A strong alkaline solution of MnSO4 reacts with oxygen in the sample
    • The liberated Iodine is titrated against a standard solution of Na₂S₂O₃

    Biological Oxygen Demand (BOD)

    • BOD measures the amount of oxygen needed for organic matter breakdown in the water, over an incubation period
    • Samples are taken for the initial and final dissolved oxygen tests to calculate the biological oxygen demand (BOD) levels
    • Procedure involves incubating samples for 5 days at 20°C to determine the final oxygen demand
    • Results are used for measuring pollution levels in water samples

    Chemical Oxygen Demand (COD)

    • Measures the amount of oxygen required to oxidise both organic and inorganic substances in water using a strong oxidizing agent like K₂Cr₂O₇.
    • This method helps gauge the pollution and contamination level in samples
    • Procedure includes reacting a test sample with a strong oxidizing agent, and titrating the remaining oxidizing agent using a standard solution
    • The chemical change leads to a colour change which can then be measured to determine the level of contamination

    Determination of Nitrate in Water

    • Nitrate content in water is determined by the reaction of nitrate ions with phenol disulfonic acid, forming a yellow colored compound.
    • The concentration of this compound is proportional to the nitrate concentration
    • A standard nitrate solution and a calibration curve are used to determine the unknown nitrate concentration
    • Procedure involves preparing PDA solution and preparing a calibration curve involving standard KNO3 solutions

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    Water Technology PDF - Unit 4

    Description

    This quiz explores the importance of water technology, focusing on the hardness of water and its implications for health, agriculture, and industry. Learn about the types of hardness, measurement units, and the impact of hard water on domestic and industrial uses.

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