Hardness of Water Overview

The calcium or magnesium ions in hard water react with stearate ions from soap to form calcium stearate.

Temporary hardness can be removed by boiling the water.

Temporary hardness can be removed by boiling, while permanent hardness cannot be eliminated through boiling.

<p>Carbon dioxide dissolves in rainwater to form carbonic acid, which reacts with limestone to produce calcium hydrogen carbonate.</p> Signup and view all the answers

<p>Boiling causes calcium hydrogen carbonate to decompose into calcium carbonate, carbon dioxide, and water.</p> Signup and view all the answers

<p>Distillation is too expensive to implement on a large scale.</p> Signup and view all the answers

<p>Washing soda reacts with Ca^2+ ions to form insoluble calcium carbonate.</p> Signup and view all the answers

<p>Cation exchange resin exchanges calcium and magnesium ions with sodium ions.</p> Signup and view all the answers

<p>Na^+^ ions replace the hard water's Ca^2+^ ions, thus softening the water.</p> Signup and view all the answers

<p>It is replenished by passing a concentrated sodium chloride solution through it.</p> Signup and view all the answers

<p>Deionised water has impurities removed but may contain dissolved gases, while distilled water is purer with all impurities and gases eliminated.</p> Signup and view all the answers

<p>The cation-exchange resin replaces Na^+^ ions with H^+^ ions.</p> Signup and view all the answers

<p>Advantage: Provides calcium for teeth and bones; Disadvantage: Wastes soap.</p> Signup and view all the answers

<p>Cl^-^ ions are replaced by OH^-^ ions in the water.</p> Signup and view all the answers

<p>The pipette should be washed and rinsed with deionised water.</p> Signup and view all the answers

<p>The ion-exchange resin process aims to produce deionised water.</p> Signup and view all the answers

<p>The burette should be filled with the EDTA solution, ensuring it's vertical, and adjusted to the zero mark without the funnel.</p> Signup and view all the answers

<p>The endpoint of the titration is indicated by a dark blue color with no tinge of wine-red.</p> Signup and view all the answers

<p>The total hardness is 300 ppm CaCO3.</p> Signup and view all the answers

<p>The buffer solution maintains the pH at 10, which is essential for the proper functioning of the indicator.</p> Signup and view all the answers

<p>Flocculation involves the coagulation of small suspended particles into larger particles for better sedimentation.</p> Signup and view all the answers

<p>Chlorine is added to sterilize the water by killing harmful microorganisms.</p> Signup and view all the answers

<p>After sedimentation, about 90% of larger particles are removed, leaving smaller suspended particles.</p> Signup and view all the answers

<p>Performing multiple titrations ensures the reliability and accuracy of the final volume measurement.</p> Signup and view all the answers

<p>To avoid trapped air bubbles that can affect the accuracy of the dissolved oxygen measurement.</p> Signup and view all the answers

<p>Sulfuric acid is needed to dissolve the precipitate and release iodine, resulting in a golden brown solution.</p> Signup and view all the answers

<p>Sodium thiosulfate serves to quantify the amount of free iodine present in the solution by reducing it to iodide.</p> Signup and view all the answers

<p>It refers to calculating the mean of two titrations where the results differ by no more than 0.1 cm^3.</p> Signup and view all the answers

<p>Air bubbles can lead to incorrect readings of dissolved oxygen concentration as they can alter sample volume.</p> Signup and view all the answers

<p>The starch indicator helps visualize the endpoint of the titration by changing color, indicating that all iodine has reacted.</p> Signup and view all the answers

<p>By converting the moles of iodine measured from the titration into moles of oxygen, and subsequently into grams and p.p.m.</p> Signup and view all the answers

<p>Dissolved oxygen levels indicate the water's ability to support aquatic life and the effectiveness of the treatment process.</p> Signup and view all the answers

<p>2.0 cm^3, 4.0 cm^3, and 8.0 cm^3.</p> Signup and view all the answers

<p>The colorimeter is used to measure the absorbance of the solutions at a wavelength of 440 nm.</p> Signup and view all the answers

<p>Add 5.0 cm^3 of 2% potassium iodide solution to each flask.</p> Signup and view all the answers

<p>Add 5 cm^3 of 5% ethanoic acid and 5.0 cm^3 of 5% potassium iodide, then fill with swimming pool water up to the mark.</p> Signup and view all the answers

<p>Total suspended solids in ppm can be calculated using the formula: $0.68 \times 2 \times 1000 = 1360$ ppm.</p> Signup and view all the answers

<p>Obtain the absorbance from the colorimeter and use the graph to find the concentration of NaOCl, then multiply by $71 / 74.5$.</p> Signup and view all the answers

<p>B.O.D is determined by measuring the difference in dissolved oxygen levels between two samples: one tested immediately and one kept in the dark for five days.</p> Signup and view all the answers

<p>Eutrophication leads to rapid algae growth that blocks sunlight, preventing photosynthesis and decreasing oxygen levels, which harms aquatic life.</p> Signup and view all the answers

<p>Rinse the sample cells with deionised water after each sample.</p> Signup and view all the answers

<p>Daylight should be used instead of artificial light.</p> Signup and view all the answers

<p>Heavy metals in water can be detected using Atomic Absorption Spectrometry (AAS).</p> Signup and view all the answers

<p>The DPD No.1 tablet reacts with chlorine to produce a color that can be compared to standards.</p> Signup and view all the answers

<p>Monitoring oxygen levels is crucial to ensure the health and survival of aquatic organisms which depend on dissolved oxygen.</p> Signup and view all the answers

<p>Conducting the B.O.D test in the dark prevents photosynthesis, ensuring that any change in dissolved oxygen is due solely to microbial activity.</p> Signup and view all the answers

<p>High B.O.D levels indicate high microbial activity, reflecting a low level of dissolved oxygen in the water.</p> Signup and view all the answers

<p>Precipitation helps remove heavy metal ions by converting them into solid particulates that can be filtered out of the water.</p> Signup and view all the answers