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Questions and Answers
A water sample is found to lather easily with soap, even after boiling. Which of the following inferences can be made about the water's hardness?
A water sample is found to lather easily with soap, even after boiling. Which of the following inferences can be made about the water's hardness?
- The water has both temporary and permanent hardness.
- The water is soft.
- The water has temporary hardness only.
- The water has permanent hardness only. (correct)
What is the primary disadvantage of using hard water in boilers within industrial settings?
What is the primary disadvantage of using hard water in boilers within industrial settings?
- Scale formation which reduces heat transfer efficiency. (correct)
- Increased solubility of gases.
- Enhanced cleaning action of detergents.
- Reduced scaling and corrosion.
In a water sample, the concentration of calcium ions ($Ca^{2+}$) is 80 mg/L and magnesium ions ($Mg^{2+}$) is 24 mg/L. What is the total hardness in mg/L as $CaCO_3$ equivalents? (Atomic weight: Ca = 40, Mg = 24, C = 12, O = 16)
In a water sample, the concentration of calcium ions ($Ca^{2+}$) is 80 mg/L and magnesium ions ($Mg^{2+}$) is 24 mg/L. What is the total hardness in mg/L as $CaCO_3$ equivalents? (Atomic weight: Ca = 40, Mg = 24, C = 12, O = 16)
- 400 mg/L
- 300 mg/L
- 104 mg/L
- 200 mg/L (correct)
What is the hydroxide ion concentration $[OH^-]$ of a solution with a pH of 4 at $25^\circ C$, given that the ionic product of water ($K_w$) is $1.0 imes 10^{-14}$?
What is the hydroxide ion concentration $[OH^-]$ of a solution with a pH of 4 at $25^\circ C$, given that the ionic product of water ($K_w$) is $1.0 imes 10^{-14}$?
Which of the following statements best describes the function of a buffer solution?
Which of the following statements best describes the function of a buffer solution?
What type of salt undergoes hydrolysis to produce a solution with a pH greater than 7?
What type of salt undergoes hydrolysis to produce a solution with a pH greater than 7?
In the Henderson-Hasselbalch equation, $pH = pK_a + log rac{[A^-]}{[HA]}$, what do $[A^-]$ and $[HA]$ represent, respectively?
In the Henderson-Hasselbalch equation, $pH = pK_a + log rac{[A^-]}{[HA]}$, what do $[A^-]$ and $[HA]$ represent, respectively?
Which of the following parameters provides an estimate of the amount of biodegradable organic matter present in a water sample?
Which of the following parameters provides an estimate of the amount of biodegradable organic matter present in a water sample?
Why is it necessary to determine the dissolved oxygen (DO) in a water sample?
Why is it necessary to determine the dissolved oxygen (DO) in a water sample?
Which of the following spectroscopic methods is commonly used for the determination of phosphorus in water samples?
Which of the following spectroscopic methods is commonly used for the determination of phosphorus in water samples?
Flashcards
Temporary Hardness
Temporary Hardness
Temporary hardness is caused by dissolved bicarbonate minerals (calcium bicarbonate and magnesium bicarbonate).
Permanent Hardness
Permanent Hardness
Permanent hardness is caused by the presence of dissolved chlorides and sulfates of calcium and magnesium, which do not precipitate out on boiling.
Disadvantages of Hard Water
Disadvantages of Hard Water
Hard water requires more soap to form lather, leads to scale formation in pipes and boilers, and can reduce the efficiency of heating systems.
pH and Buffer Solutions
pH and Buffer Solutions
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Hydrolysis of Salt
Hydrolysis of Salt
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Henderson-Hasselbalch Equation
Henderson-Hasselbalch Equation
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Biological Oxygen Demand (BOD)
Biological Oxygen Demand (BOD)
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Chemical Oxygen Demand (COD)
Chemical Oxygen Demand (COD)
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Spectroscopic Determination
Spectroscopic Determination
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Study Notes
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Water hardness can be temporary or permanent.
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Temporary hardness is caused by dissolved bicarbonates which can be removed by boiling.
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Permanent hardness is caused by dissolved sulfates and chlorides, which cannot be removed by boiling.
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Hard water has disadvantages, including scaling in pipes and reduced soap effectiveness.
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Determining water hardness involves titration with EDTA.
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Water undergoes dissociation, producing hydrogen and hydroxide ions.
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The ionic product of water (Kw) is the product of hydrogen and hydroxide ion concentrations.
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pH is a measure of the acidity or alkalinity of a solution.
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Buffer solutions resist changes in pH upon addition of acid or base.
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Hydrolysis of salt is the reaction of a salt with water, which affects the pH of the solution.
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The Henderson-Hasselbalch equation relates pH, pKa, and the ratio of conjugate base to acid concentrations in a buffer solution.
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Acidity, alkalinity, dissolved oxygen, and carbon dioxide are important parameters in water quality analysis.
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Dissolved and suspended solids are also key indicators of water quality.
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Chemical Oxygen Demand (COD) measures the amount of oxygen required to oxidize all chemicals in water.
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Biological Oxygen Demand (BOD) measures the amount of oxygen consumed by microorganisms in water.
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Spectroscopic methods can determine phosphorus, nitrate, and nitrite concentrations in water.
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