Quizlet - Lime Softening Flashcards by Matthew Fritz

What is alkalinity?
a. A laboratory procedure used to estimate the minimum or ideal coagulant dose required to achieve certain water quality goals
b. A process used to kill disease-causing organisms
c. A solution or liquid whose chemical make-up neutralizes acids or bases without a great change in pH
d. The capacity of water to neutralize acids

d. The capacity of water to neutralize acids

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If the methyl orange alkalinity of water equals or exceeds total hardness, all of the hardness is?
a. Non-carbonate hardness
b. Carbonate hardness
c. Pseudo hardness
d. Negative non-carbonate hardness

b. Carbonate hardness

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When sodium carbonate is introduced into the water treatment process, what adjustment is typically required for the lime dosage?
a. Increase the lime dosage
b. No adjustment needed
c. Decrease the lime dosage
d. Double the lime dosage

c. Decrease the lime dosage

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Calcium Hardness + Magnesium Hardness = ?
a. Total Hardness
b. Scale
c. Non-carbonate Hardness
d. Carbonate Hardness

a. Total Hardness

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Non-carbonate hardness equals:
a. Calcium and magnesium hardness
b. Carbonate hardness minus total alkalinity
c. Total hardness minus hydroxide alkalinity
d. Total hardness minus total alkalinity

d. Total Hardness minus Total Alkalinity

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The range of pH is:
a. 1 - 14
b. 1 - 7
c. 1 - 12
d. 0 - 12
e. 0 - 14

e. 0 - 14

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Which chemical is slaked lime?
a. Ca(OH)2
b. Ca(HCO3)2
c. CaCO3
d. Ca(H20)2

a. Ca(OH)2

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Why would soda ash be added to a lime softening process?
a. Increase silica removal
b. Gives higher dissolved solids to “salt out” carbonates
c. Provides better floc formation and settling
d. Provides alkalinity to remove additional hardness

d. Provides alkalinity to remove additional hardness

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Why is carbonate hardness considered temporary in nature?
a. It can be easily precipitated out
b. It is caused by organic materials
c. It does not affect pH levels
d. It is always present in water

a. It can be easily precipitated out

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Carbonates in water produce:
a. Temporary hardness
b. Permanent hardness
c. Acidity
d. Alkalinity

a. Temporary hardness

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When the alkalinity of water its total hardness, which type of hardness is primarily present?
a. Non-carbonate hardness
b. Temporary hardness
c. Carbonate hardness
d. Permanent hardness

c. Carbonate hardness

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Below what pH does water no longer have a measurable alkalinity?
a. 3.7
b. 4.1
c. 4.5
d. 4.9

c. 4.5

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What effect does the addition of sodium aluminate have on the overall pH of treated water?
a. The pH decreases
b. The pH remains unchanged
c. The pH increases
d. The pH fluctuates unpredictably

c. The pH increases

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What is the primary concern for water treatment plant operators regarding the presence of sulfates in water?
a. They can lead to corrosion of pipes
b. They contribute to increased alkalinity
c. They have a laxative effect
d. They enhance the effectiveness of chlorine

c. The have a laxative effect

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The pH scale ranges from 0 (most acidic) to 14 (most basic). Water’s pH is _____.
a. 5.0
b. 7.0
c. 9.0

b. 7.0

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What issue is often encountered in residential water heaters that utilize water softened with lime?
a. Corrosion of the tank due to high acidity
b. Scaling of heating elements from calcium carbonate precipitation
c. Increased energy consumption from inefficient heating
d. Frequent breakdowns of the heating system

b. Scaling of heating elements from calcium carbonate precipitation

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Most colloidal material from the raw water should be removed by what method in a properly designed and operated treatment plant?
a. Sedimentation
b. Filtration
c. Recarbonization
d. Disinfection

a. Sedimentation

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If you need to lower the pH, which of the following would you use?
a. H2SO4
b. Liquid polymer
c. NaOH
c. Ca(OH)2

a. H2SO4

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The pH scale ranges from 0 to 14. A low numerical pH value is associated with a high concentration of H+ (or low OH-) and a high pH value with a low concentration of H+ (or high OH-). Which statement about pH is correct?
a. An alkaline solution has a low pH and low concentration of H+
b. An acidic solution has a low pH and high concentration of H+
c. An acidic solution has a high pH and low concentration of H+

b. An acidic solution has a low pH and a high concentration of H+

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What happens to the pH and alkalinity of the sludge after lime is added to it?
a. The pH goes down and the alkalinity goes up
b. The alkalinity goes down and the pH goes up
c. The pH goes up and the alkalinity goes up
d. None of the above

c. The pH goes up and the alkalinity goes up

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Below a pH of 8.3, which of the following does not exist?
a. CO2
b. P Alkalinity (PA)
c. SO2
d. HOCL

b. P Alkalinity (PA)

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During lime softening, lime is added to remove carbonate hardness. Which of the following would be added to remove non-carbonate hardness?
a. Alum
b. Chlorine
c. Soda ash (sodium bicarbonate)
d. Polyaluminum chloride

c. Soda ash (sodium bicarbonate)

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What adjustment is typically made to the lime dosage when the alum dosage is reduced during water treatment?
a. Lime dosage is increased
b. Lime dosage remains the same
c. Lime dosage is decreased
d. Lime dosage is eliminated

c. Lime dosage is decreased

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Alkalinity caused by hydroxide ions is called:
a. Carbonate alkalinity
b. Bicarbonate alkalinity
c. Total alkalinity
d. Hydroxyl alkalinity

d. Hydroxyl alkalinity

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What is the recommended range for pH levels in drinking water according to the Secondary Maximum Contaminant Level (SMCL)? a. 5.0 - 6.5 b. 6.5 - 8.5 c. 7.0 - 9.0 d. 8.0 - 10.0

b. 6.5 - 8.5

The pH of a liquid solution is a measure of which of the following? a. Hydrogen ion activity b. Hydroxyl ion material c. Dissolved salt content d. Electrical conductivity

a. Hydrogen ion activity

Excess lime is used to remove Mg but adds Ca2+ hardness in the process. What is the subsequent process to remove this hardness? a. Dual-filtering media b. Refurbishing c. Sedimentation d. Recarbonization

d. Recarbonization

Which two chemicals, when mixed, can lead to the formation of toxic gases and should therefore be kept separate during water treatment? a. Chlorine and Ammonia b. Lime and Alum c. Sodium Hypochlorite and Sulfuric Acid d. Calcium Carbonate and Magnesium Sulfate

a. Chlorine and Ammonia

When the total hardness of water exceeds its alkalinity, what does the difference represent in terms of water chemistry? a. Carbonate hardness b. Non-carbonate hardness c. Temporary hardness d. Permanent hardness

b. Non-carbonate hardness

OH alkalinity is found from which equation? a. 2M - P = OH b. 2P - M = OH c. P x M = OH d. 2OH = P - M

b. 2P - M = OH

The _____ process raises the pH above 10.6 and often requires recarbonization to bring the pH back to a level that is not corrosive. a. excess lime treatment b. split treatment c. delayed dose treatment d. saturated dose treatment

a. excess lime treatment

What substance is commonly introduced during the recarbonization process to effectively reduce both, pH and alkalinity in water treatment? a. Sodium bicarbonate b. Calcium bicarbonate c. Carbon dioxide d. Magnesium sulfate

c. Carbon dioxide

What occurs when the pH of water is elevated to 11 or above due to lime addition? a. Calcium Carbonate precipitates form b. Sodium Bicarbonate dissolves c. Magnesium Hydroxide precipitates form d. Alum reacts with lime

c. Magnesium Hydroxide precipitates form

At what level does carbonate alkalinity (CA) typically begin to be present in water? a. Below 6.5 b. Between 6.5 and 8.3 c. Above 8.3 d. Always present regardless of pH

Above pH of 8.3

Which two categories of hardness are combined to determine the total hardness of water? a. Temporary and permanent hardness b. Carbonate and non-carbonate hardness c. Calcium and sodium hardness d. Magnesium and sulfate hardness

b. Carbonate and Non-carbonate hardness

Which of the following is is primarily responsible for contributing to Non-carbonate Hardness in water? a. Calcium b. Sulfates c. Bicarbonates d. Nitrates

b. Sulfates

What is the purpose of a water softener in a boiler feedwater system? a. To remove impurities from the water b. To increase the temperature of water c. To decrease the temperature of water d. To remove minerals that can cause scaling

d. To remove minerals that can cause scaling

Which treatment chemical can be used to lower pH? a. Carbon dioxide b. Lime (calcium hydroxide) c. Potassium Permanganate d. Chlorine

Carbon dioxide

Which type of hardness is considered permanent hardness? a. Carbonate hardness b. Non-carbonate hardness c. Calcium hardness d. Magnesium hardness

b. Non-carbonate hardness

Ca(OH)2 is called: a. Quicklime b. Slaked lime c. Limestone d. Gypsum

b. Slaked lime

Non-carbonate hardness can be removed by which of the following? 1. Heating 2. Distillation 3. Precipitation Softening Process 4. Ion Exchange Process a. 1 and 2 b. 1 and 3 c. 2 and 4 d. 3 and 4

d. 3 and 4

What is the primary reason for adjusting the pH of water after precipitation of hardness due to lime treatment? a. To enhance the solubility of calcium ions b. To facilitate the removal of magnesium ions c. To minimize the potential for scaling in distribution systems d. To increase the alkalinity of the water

c. To minimize the potential for scaling in distribution systems

Surface water pH is generally: a. Exactly 7.0 units b. 4.0 to 6.0 units c. 6.5 to 8.5 units d. 8.5 to 9.5 units

c. 6.5 to 8.5 units

Non-carbonate hardness is caused by: a. Alkalinity b. Calcium c. Bicarbonate ions d. Sulfates

d. Sulfates

What effect does increasing the dosage of lime have on the pH level of treated water? a. The pH level will decrease b. The pH level will remain unchanged c. The pH level will increase d. The pH level will fluctuate unpredictably

c. The pH level will increase

What are the primary reasons for implementing water softening processes in treatment facilities? a. Hard water leads to increased energy consumption in heating systems b. Hard water enhances the effectiveness of detergents c. Hard water improves the taste of drinking water d. Hard water contributes to corrosion in plumbing systems

a. Hard water leads to increased energy consumption in heating systems

Which method is commonly used to quickly assess the hardness of water? a. Using a pH meter b. Conducting a soap test c. Measuring turbidity d. Performing a conductivity test

b. Conducting a soap test

The presence of Bicarbonate, Carbonate, and Hydroxide contributes to the: a. Alkalinity of water b. Acidity of water c. Silica content of water d. All of the answers listed

a. Alkalinity of water

If the total hardness of water is greater than its total alkalinity, the carbonate hardness will be equal to? a. Total alkalinity b. Total hardness c. Total hardness and total alkalinity d. Non-carbonate hardness

a. Total alkalinity

Which one of the following statements related to testing of water for municipal use is correctly applicable? a. Pseudo-hardness is due to the presence of fluoride in water b. When alkalinity is equal to or greater than total hardness, Carbonate hardness (in mg/L) = Total hardness (in mg/L) c. Bicarbonate alkalinity = Total alkalinity - (Carbonate alkalinity - Hydroxide alkalinity) d. Hydroxide alkalinity = Carbonate alkalinity + Bicarbonate alkalinity

b. When alkalinity is equal to or greater than total hardness, Carbonate hardness (in mg/L) = Total hardness (in mg/L)

What typically happens to the pH, of a pH neutral water sample when alum is added? a. The pH increases b. The pH decreases c. Alum does not affect sample pH

b. The pH decreases

At what stage in the water treatment process is carbon dioxide typically introduced to enhance the removal of hardness? a. After filtration b. During sedimentation c. Before filtration d. During chlorination

c. Before Filtration

What adjustment is typically required to the lime dosage when the dosage of alum us decreased during water treatment? a. Lime dosage is decreased b. Lime dosage remains the same c. Lime dosage is increased d. Lime dosage is eliminated

a. Lime dosage is decreased

What is typically observed in water when the pH falls below 6.5? a. Increased levels of bicarbonate ions b. Presence of dissolved oxygen c. Higher concentrations of carbon dioxide d. No significant change in alkalinity

c. Higher concentrations of carbon dioxide

Why is discharging lime-soda ash sludge to sanitary sewers not a widely used method? a. Sewers can become plugged b. Acts as a coagulant on wastewater influent c. Reduces the pH of the raw wastewater d. Corrosion will occur in sewer lines

a. Sewers can become plugged

What happens when lime is fed to water for corrosion control? a. Alkalinity is decreased b. CO2 does not change c. Turbidity is decreased d. pH is increased

d. pH is increased

Which compound is commonly used in conjunction with lime to effectively eliminate non-carbonate hardness in water treatment processes? a. Calcium Chloride (CaCl2) b. Soda Ash (Na2CO3) c. Alum (Al(SO4)2) d. Magnesium Sulfate (MgSO4)

b. Soda Ash (Na2CO3)

What is the primary method of disposing of lime sludge generated from the water treatment process? a. Incineration b. Sanitary landfill c. Ocean dumping d. Agricultural land application

b. Sanitary landfill

Which of the following is a benefit of using lime in water softening processes? a. Reduction of heavy metal concentrations b. Increase in water temperature c. Improvement of taste and odor d. Removal of dissolved gases

a. Reduction of heavy metal concentrations

What type of alkalinity predominates in water when the pH is below 8.3? a. Bicarbonate alkalinity b. Carbonate alkalinity c. Hydroxide alkalinity d. Total alkalinity

a. Bicarbonate alkalinity

Lime-Soda Softeners use ____ to add to the water, causing the scale-forming dissolved solids. a. Calcium hydroxide b. Sodium chloride c. Sodium carbonate d. Both, A and C e. All of the above

d. Both, A and C (Calcium hydroxide and Sodium carbonate)

CaO is called: a. Quicklime b. Slaked lime c. Limestone d. Calcite

a. Quicklime

The total alkalinity is a measure of: a. OH-, Carbonate, and Bicarbonate b. Carbonate and Bicarbonate c. Bicarbonate d. OH- and Bicarbonate

a. OH-, Carbonate, and Bicarbonate

The by-product of slaked lime is? a. Grit b. Sand c. Heat d. Alkalinity

c. Heat

Total Hardness is _____ Total Alkalinity. a. Greater than b. Less than c. Equal to d. No the same as

d. Not the same as

Logarithm of the reciprocals of the hydrogen ion concentration: a. Mole b. Millimole c. pH d. pKa

c. pH

Lime that has not reacted with water (not hydrated) is referred to as Quicklime. This is a very dangerous material that can cause chemical burns. This is denoted as: a. CaO b. Ca(OH)2 c. H2O d. O2

a. CaO

What method can water treatment plants employ to optimize lime usage while effectively managing magnesium hardness? a. Coagulation b. Split treatment c. Filtration d. Sedimentation

b. Split treatment

The alum, when mixed with water as a coagulant: a. Does not affect pH b. Decreases the pH value of water c. Increases the pH value of water d. None of these

b. Decreases the pH value of water

Alkalinity refers to the acid neutralizing capability of a solution. Which of the following chemicals, when added to a solution, would not increase the buffer capacity of the solution? a. NH4Cl b. NaHCO3 c. Na2CO3 d. K2HPO4

a. NH4Cl

What is the most common method for disposing of lime sludge? a. Storage in lagoons (lagooning) and later disposal in a landfill b. Sanitary sewer c. Blended with natural water bodies d. Dryer unit and then an incinerator

a. Storage lagoons (lagooning) and later disposal in a landfill

What is (typically) the dominant form of alkalinity in natural waters? a. Bicarbonate (HCO3-) b. Carbonate (CO3^2-) c. Carbonic Acid (H2CO3)

a. Bicarbonate (HCO3-)

Calcium and Magnesium Bicarbonates and Carbonates create what kind of hardness? a. Temporary b. Permanent

a. Temporary

Which chemical is commonly utilized to lower both, pH and alkalinity levels in water treatment processes? a. Sodium Hydroxide b. Calcium Carbonate c. Carbon Dioxide d. Sodium Bicarbonate

c. Carbon Dioxide

The presence of soluble salts of magnesium and calcium in the form of chlorides and sulfides in water: a. Permanent hardness b. Temporary hardness c. Total hardness d. Maximum hardness

a. Permanent hardness

The formula of the hydroxide ion is: a. OH- b. OH+ c. H3O+ d. H3O- e. None of the above

a. OH-

The process of adding carbon dioxide to a softened water with the objective of lowering the pH and re-establishing alkalinity is called: a. pH adjustment b. Oxidation c. Recarbonization d. Desulfurization

c. Recarbonation

Carbonate hardness is: a. Bicarbonate + Carbonate when expressed as mg/L as CaCO3 b. The Total Alkalinity or Total Hardness, whichever is Less c. The sum of monovalent cations in the water sample d. Monochloramine + Dichloramine concentration

b. The Total Alkalinity or Total Hardness, whichever is Less

The pH meter used in the lab and commonly seen in clinical laboratories measures hydrogen activity through the use of: a. Coulometry b. Spectrophotometry c. Ion selective electrode d. Electrophoresis

c. Ion selective electrode

What is the primary effect of adding lime to water in terms of chemical composition? a. It decreases the hardness of water b. It lowers the pH and alkalinity c. It raises the pH and alkalinity d. It has no effect on water chemistry

c. It raises the pH and alkalinity

Below a pH of 8.3, what is the ONLY type of alkalinity present in water? a. P alkalinity b. Carbonate alkalinity c. Hydroxide alkalinity d. Bicarbonate alkalinity (HCO3)

d. Bicarbonate alkalinity (HCO3)

Hard water is undesirable and is often softened because hard water: a. Is too viscous for regular uses b. Contains trace amounts of toxic substances c. Forms insoluble precipitates when boiled or used with soap d. Cannot be used efficiently by the body due to dissolved impurities e. Evaporates more rapidly than soft water

c. Forms insoluble precipitates when boiled or used with soap

What is a disadvantage of lime softening? a. Removes sulfates b. THM formation c. Removal of radioactivity d. Both, A and B

b. THM formation

The predominant carbonate alkalinity form in a surface water with a pH between 7 and 8 is: a. Calcium carbonate b. Bicarbonate c. Carbonate d. Hydroxide e. Is unpredictable

b. Bicarbonate

The definition of pH is: a. The negative logarithm of the hydrogen ion activity b. The positive logarithm of the hydrogen ion activity c. The negative logarithm of the hydroxyl ion activity d. The positive logarithm of the hydroxyl ion activity

a. The negative logarithm of the hydrogen ion activity

The primary advantage of hot lime softening over cold lime softening is: a. Increased hardness/alkalinity removal due to increased solubility b. Reduced lime addition c. Increased gypsum removal d. No need for filtration

a. Increased hardness/alkalinity removal due to increased solubility

What processes are typically employed to eliminate pin floc from treated water? a. Coagulation and sedimentation b. Recarbonization and filtering c. Chlorination and aeration d. Flocculation and disinfection

b. Recarbonization and filtering

Alkalinity is found by experimentally determining how much acid it takes to lower the pH of water to: a. 8.0 b. 7.8 c. 4.5 d. 7.0 e. 3.5

c. 4.5

Adding lime to raise the pH of the raw water to 11 or more, results in what reaction taking place? a. Bicarbonate precipitates form b. Calcium precipitates form c. Magnesium hardness precipitates form

c. Magnesium precipitates form

A pH Above _____ is needed to form the magnesium hydroxide precipitate. a. 9.0 b. 9.2 c. 9.5 d. 10.6

d. 10.6

Total alkalinity is defined as the amount of acid required to lower the pH of the sample to: a. 4.5 b. 7.1 c. 8.3 d. 9.2

a. 4.5

Which sludge disposal method is most economical for lime-soda ash softening plants? a. Disposal into the sewage system b. Sand drying beds c. Lagoons d. Landfill the sludge

c. Lagoons

What transformation occurs when lime is introduced to water containing bicarbonate alkalinity? a. Bicarbonate alkalinity is converted to sulfate alkalinity b. Bicarbonate alkalinity is converted to carbonate alkalinity c. Bicarbonate alkalinity is converted to chloride alkalinity d. Bicarbonate alkalinity remains unchanged

b. Bicarbonate alkalinity is converted to carbonate alkalinity

Temporary water hardness is caused by: a. Bicarbonates b. Sulfates c. Hydroxides d. Chlorides

a. Bicarbonates

Which type of hardness usually calls for a two-stage softening process? a. Calcium hardness above 100 mg/L b. Magnesium hardness c. Non-carbonate haedness d. Carbonate hardness

b. Magnesium hardness

Adding sodium aluminate to water will _____. a. Lower pH b. Increase pH c. Balance pH d. Cause a negative L. I.

b. Increase pH

What occurs when the addition of lime increases the pH of water to 10, affecting calcium ions? a. Calcium ions remain soluble b. Calcium ions precipitate as calcium carbonate c. Calcium ions are completely removed from the water d. Calcium ions increase in concentration

b. Calcium ions precipitate as calcium carbonate

Lime softening in the presence of calcium and magnesium will form which magnesium precipitate? a. MgSO4 b. MgCO3 c. Mg(OH)2 d. MgCO2

c. Mg(OH)2

_____ is a modification of the excess-lime process and is used to reduce the amount of chemicals required for softening. a. Split treatment b. Delayed dose treatment c. Timed mixing treatment d. Saturated dose treatment

a. Split treatment

What is released during the process of slaking lime that can affect the temperature of the surrounding environment? a. Carbon dioxide b. Heat c. Oxygen d. Hydrogen

b. Heat

The correct formula for Sodium Hydroxide would be: a. SOH b. NaH c. NaOH d. Na(OH)2

c. NaOH

What is the common name for the chemical compound represented by the formula Ca(OH)2, which is often used in water treatment processes? a. Quicklime b. Slaked lime c. Calcium carbonate d. Sodium hydroxide

b. Slaked lime

Which chemical component is primarily responsible for increasing the viscosity of lime sludge, complicating the dewatering process? a. Calcium b. Sodium c. Magnesium d. Potassium

c. Magnesium

Hardness is defined as the sum of the _____ and _____ ions, although any divalent metal ion can contribute to hardness. a. Calcium and Sulfate b. Calcium and Magnesium c. Struvite and Silver d. Magnesium and Sodium

b. Calcium and Magnesium

What term is used to describe water that contains a high concentration of dissolved minerals, particularly calcium and magnesium, typically exceeding 200 mg/L? a. Soft water b. Hard water c. Distilled water d. Deionized water

b. Hard water

Of the following types of hardness, which of them is the most difficult to remove? a. Analytical hardness b. Carbonate hardness c. Non-carbonate hardness d. Temporary hardness

c. Non-carbonate hardness

Adding alum to the water ______ the pH. a. stabilizes b. lowers c. increases d. maintains

b. lowers

Total alkalinity is measured: a. Using methyl orange indicator and sulfuric acid b. To ensure that it doesn't exceed 2500 ppm c. To control dissolved oxygen d. By using phenolphthalein and sulfuric acid

a. Using methyl orange indicator and sulfuric acid

What is the typical range of water hardness that can be achieved through the process of lime softening alone? a. 10 - 20 mg/L b. 30 - 40 mg/L c. 50 - 60 mg/ l d. 70 - 80 mg/L

b. 30 - 40 mg/L

Hydroxide added to the bicarbonate buffer system causes the formation of which? a. Water b. Carbon dioxide c. Water and Carbon dioxide d. Bicarbonate and Carbonate

d. Bicarbonate and Carbonate

Liming affects pH because: a. (CO3)2- in lime combines with H+ to form CO2 and H2O, thereby consuming protons b. Ca2+ in lime is a base and neutralizes H+ c. Adding lime increases the adsorption of H+ to the cation exchange complex d. None of the above

a. (CO3)2- in lime combines with H+ to form CO2 and H2O thereby consuming protons

During lime-softening, we can remove calcium in the water (Ca+2) by adding calcium (lime). How is this possible? a. Lime lowers the pH, which allows CaCO3(s) to precipitate b. Lime decreases the alkalinity, which allows CaCO3(s) to precipitate c. Lime raises the pH, which allows CaCO3(s) to precipitate d. Lime increases the viscosity, which allows CaCO3(s) to precipitate e. It's not possible; you're making that up

c. Lime raises the pH, which allows CaCO3(s) to precipitate