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CWEA - pH/Acidity/Alkalinity Flashcards | StudBud
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CWEA - pH/Acidity/Alkalinity
CWEA - pH/Acidity/Alkalinity
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1
How many buffers are recommended for proper calibration of a pH meter?
4
2
1
3
2
The pH endpoint for the US EPA Method 305.1 (Acidity) is
4.2
3.7
8.2
8.7
3
The endpoint for acidity may be determined by titrating to a
Potentiometnic endpoint of 5.5
Metacresol purple indicator endpoint of 4.2
pH of 7.0
Phenolphthalein indicator endpoint of 8.3
4
SS or precipitates formed during titration may cause sluggish electrode response. Offset this slow electrode response by
Adding some polymer to aid coagulation
Allowing the sample to sit for 10 minutes between each titrant addition
Slowly adding drops of titrant as the endpoint pH is approached
Stirring the sample faster
5
Alkalinity is a measure of the
Capacity to neutralize bases
Capacity to neutralize acids
Change in pH in aerobic samples
Increase in salinity
6
Soaps, oily matter, suspended solids, or precipitates may coat pH electrodes and cause sluggish response.
Clean the electrodes occasionally between titrations
Pretreat the sample with trichlorotriflouroethane to remove oily residue
Wash the electrode with alkaline-based titrant daily
Filter the sample before analysis
7
Compared to a solution with a pH of 4, an acid solution with a pH of 2 is
10 times as acidic
Twice as alkaline
100 times as acidic
Twice as acidic
8
The definition of pH is
The negative logarithm of the hydroxyl ion activity
The positive logarithm of the hydrogen ion activity
The positive logarithm of the hydroxyl ion activity
The negative logarithm of the hydrogen ion activity
9
Neutral pH at 25 °C is 7.0. Neutral pH of a sample at 0 °C
Stays the same
Decreases
Increases
Fluctuates
10
What three principle forms of alkalinity are present in many waters?
Carbonate. phenolphthalein, and hydroxide
Carbon dioxide, hydroxide, and bicarbonate
Carbonate, hydroxide, bicarbonate
Carbon dioxide, carbonate, and phenol
11
In the acidity titration method, phenolphthalein is used in the process of titration as a(n)
Indicator
Oxidizer
Neutralizer
Coagulant
12
The correct preservation and hold time for samples being stored before acidity or alkalinity measurements is
7 days at 4 °C
No hold time; analyze immediately at > 4 °C
14 days at 0 °C
14 days at 4 °C
13
Which of the following is the correct way to calculate acidity?
Acidity, mg/L = (Vtitrant, mL x NNaOH x 50,000)/Vsample, mL
Acidity, mg/L = (Vsample, mL x NNaOH x 50,000)/Vtitrant, mL
Acidity, mg/L = (Vtitrant, mL x NNaOH x 10,000)/Vsample, mL
Acidity, mg/L = (Vsample, mL x NNaOH x 10,000)/Vtitrant, mL
14
For a sample known to be basic, which buffers should be used to standardize the pH meter before pH measurement?
4 and 7
7 and 10
1 and 5
11 and 13
15
The most common cause of pH electrode fouling is coating with
Volatile solids
Grity material
Oily material and/or precipitated solids
Dissolved solids
16
A sample has a pH of 6.5 at 25 °C. This sample can be said to be
Basic
Alkaline
Neutral
Acidic
17
Which parameter is responsible for changing the slope of a pH meter calibration?
Temperature
Conductivity
Salinity
Resistivity
18
What is the effect of anaerobic conditions on the pH of wastewater
Has no effect
Raises the pH
Lowers the pH
Buffers the pH
19
When using a pH meter that does not have auto temp compensation, adjust the sample temperature before titration to
20 °C ± 2 °C
20 °C ± 1 °C
25 °C ± 2 C
23°C ± 2°C
20
How often should a pH meter be calibrated to ensure accuracy?
Weekly
Twice a day
Monthly
Daily
21
The pHs of 6 samples are 6.0, 7.5. 6.9. 5.2, 8.9, and 8.5. We may conclude that the pH of the composite sample is
7.2
4.2
8.9
pH values cannot be averaged
22
What should an analyst do with the fill hole on refillable nonsealed pH electrodes during pH measurements?
Immerse it in sample
Leave it covered
Leave it uncovered
Immerse it in buffer
23
Which of the following is the correct way to calculate alkalinity?
Alkalinity, mg/L = (Vsample, mL x NNaOH x 50,000)/Vtitrant, mL
Alkalinity, mg/L = (Vtitrant, mL x NNaOH x 50,000)/Vsample, mL
Alkalinity, mg/L = (Vtitrant, mL x Nacid x 50,000)/Vsample, mL
Alkalinity, mg/L = (Vsample, mL x Nacid x 50,000)/Vtitrant, mL
24
The potentiometric endpoint for total alkalinity is a pH of
3.7
4.3
4.5
8.3
25
Bromcresol green indicator solution has a pH endpoint of
3.7
4.3
4.5
8.3
26
Which of the following has the strongest effect on a pH measurement?
Temperature
Oxidants
Turbidity
Colloidal suspension
27
The acid or basic condition of a sample is expressed by its
Alkalinity
Conductivity
pH
Acidity
28
The acidity of a sample is measured by the quantity of
A weak base required to bring the sample to a designated pH
A strong base required to bring the sample to a designated pH
A strong acid required to bring the sample to a designated pH
A weak acid required to bring the sample to a designated pH
29
The hold time for a pH sample is
24 hours
48 hours
None, analyze immediately
12 hours
30
The standard titrant for U.S. EPA Method 310.1 (Alkalinity) is
0.01 M EDTA
0.02 N H2SO4 or HCI for alkalinity concentrations <1000 mg CaCO3/L
1.0 N H2SO4 or HCI for alkalinity concentrations > 1000 mg CaCO3/L
0.1 /n Na2S2O3
31
Adjust the sample volume used for alkalinity titration to avoid
Having a CaCO3 concentration greater than 10 000 mg/L
Having a titration volume greater than 50 mL
Having a total titration time greater than 15 minutes
Using too much of the sample
32
When no phenolphthalein alkalinity is found in a wastewater sample, all of the remaining alkalinity present is
Hydroxide
Carbon dioxide
Bicarbonate alkalinity
Carbonate alkalinity
33
Using a 50-mL sample, what range does the U.S. EPA Method 310.1 (AIkalinity: Titrimetric) cover
10 to 1000 mg/L as CO2
0.1 to 100 mg/L as CaCO3
500 to 1000 mg/L as CaCO3
10 to 1000 mg/L as CaCO3
34
Report pH measurements in standard units to the nearest
0.01
0.1
0.001
1.0
35
Results of an acidity measurement are reported as milligrams per liter CaCO3 and should include the
Type of analysis equipment used
Color indicator used
Specific pH endpoint used
Sample temperature at time of analysis
36
Select the appropriately sized vessel/container for alkalinity titrations to
Leave room for a maximum addition of 100 mL of titrant
Provide the largest possible surface area for complete mixing
Keep the air space above the solution to a minimum
Allow space to mix the sample at a high speed without splashing
37
Acidity in wastewater can be caused by
Formation of colloidal particles in the collection system
Use of lime in industrial discharges
Carbonates in the wastewater
Septic anaerobic conditions in the collection system
38
The pH endpoint for a total alkalinity test is
4.5
7.0
9.0
5.5
39
During the acidity measurement, stir the sample with a magnetic stir bar at a rate that
Allows SS to settle
Thoroughly but gently mixes the sample and titrant with no splashing
Allows the sample to splash excessively, thereby entraining air
Causes desired sample surface disturbance
40
Alkalinity is reported as
micrograms per liter CaCO3
milligrams per liter CaCO3
milligrams per liter CO3
milligrams per kilograms CaCO3
41
The pH endpoints used for a total acidity measurement accd to Standard Methods 2310 B (Acidity: Titration Method) are
8.7 and 9.7
4.2 and 8.2
4.2 and 8.7
3.7 and 8.3
42
To avoid the gain or loss of dissolved gases contributing to the acidity or alkalinity of a sample
Warm the sample to 35 °C
Bubble air through the solution
Avoid vigorous shaking or mixing of the sample
Add a buffer solution
43
What type of sample should be collected for pH testing?
A regulated sample
A composite sample
A composite sample
A grab sample
44
Acidity samples containing free chlorine residual are pretreated by adding one drop of
0.1 M Na2S2O3
0.1 N DPD
0.1 N NaOH
0.1 N Na2SO4
45
Which temperature measurement should always be reported to the nearest degree Celsius for each pH measurement?
Buffer
Equipment
Ambient
Sample
46
In the titration method for alkalinity, the acid titrant is standardized with which solution?
CaCO3
Na2CO3
NaOH
NaHCO3
47
The concentration of hydrogen ions is most closely related to
Buffer capacity
Normality
pH
Alkalinity
48
The pH reading is considered stable and drift free when
The pH reading changes fewer than 0.5 standard pH units within O seconds
There is no further change in the temperature reading
The pH reading begins to slowly rise or drop in the opposite direction
The pH reading changes fewer than 0.1 pH units
49
Fresh pH buffer solutions should be prepared
Per manufacturer's specifications
Daily
Monthly
Weekly
50
The standard titrant for acidity using Standard Methods 2310 B. (Acidity: Titration Method) is
0.02 N Ca(OH)2
0.02 N NaOH
0.2 M NaOH
0.02 N CaCl,
51
Bromcresol green, methyl red, and metacresol purple indicators are used in what test?
Alkalinity
MPN test for fecal coliform
Membrane filter test for fecal coliform
Hardness
