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WW Lab Analyst Study guide
Terms in this set (56)
The pH measurement is temperature dependent. Which temperature measurement should always be reported to the nearest degree Celsius for each pH measurement?
Report pH measurements in standard units to the nearest
Neutral pH at 25 C is 7.0. Neutral pH of a sample at 0C does what?
The acid or basic condition of a sample is expressed by its
What is the effect of anaerobic conditions on the pH of wastewater
Lowers the pH
The pH reading is considered stable and drift free when
the pH changes fewer than 0.1 units
The most common cause of pH electrode fouling is coating with
Oily material and/or precipitated solids
Fresh pH buffer solutions should be prepared
What should an analyst do with the fill hole on refillable nonsealed pH electrodes during pH measurements?
leave it uncovered
The hold time for a pH sample is
none, analyze immediately
To avoid the gain or loss of dissolved gases contributing to the acidity or alkalinity of a sample
avoid vigorous shaking or mixing of the sample
Acidity samples containing free chlorine residual are pretreated by adding one drop of
The endpoint for acidity may be determined by titrating to a
phenolphthalein indicator endpoint of 8.3
Using a 50-mL Sample, what range does the US EPA Method 310.1 (Alkalinity: Titrimetric) cover
10-1000mg/L as CaCO3
Suspended solids present in the sample or precipitates formed during titration may cause sluggish electrode response. Offset this slow electrode response by
Slowly adding drops of titrant as the endpoint pH is approached. Stirring the sample faster is incorrect because this could increase the dissolved gasses in the sample. Slowly titrating allows time for the titrant to fully react with the sample and for the pH electrode to respond. However, waiting 10 minutes between each titrant addition is excessive.
The acidity of a sample is measured by the quantity of
a strong base required to bring the sample to the designated pH
During the acidity measurement, stir the sample with a magnetic stir bar at a rate that
Thoroughly but gently mixes the sample and titrant with not splashing
The standard titrant for acidity using Standard Methods 2310 B (Acidity : Titration Method) is
The correct preservation and hold time for samples being stored before acidity or alkalinity measurements is
14 days at 6 degrees C
Results of an acidity measurement are reported as milligrams per liter CaCO3 and should include the
specific pH endpoint used
The pH endpoint for the US EPA Method 305.1 (Acidity) is
The pH endpoints used for a total acidity measurement according to Standard Methods 2310B (Acidity: Titration Method) are
3.7 and 8.3
What is the correct way (formula) to calculate acidity
(Titrant used, mL x N of NaOH Titrant x 50000)/Sample Vol, mL
Alkalinity is reported as
milligrams per liter CaCO3
What is the correct way to calculate alkalinity
(Acid Titrant Used, mL x N of Acid Titrant x 50000)/Sample Volume, mL
Bromcresol green indicator solution has a pH endpoint of
Soaps, oily matter suspended solids, or precipitates may coat pH electrodes and cause sluggish response. To overcome these interferences
Clean the electrodes occasionally between titrations
Adjust the sample volume used for Alkalinity titration to avoid
having a titration volume greater than 50 mL
When using a pH meter and electrode that do not have automatic temperature compensation, adjust the sample temperature before titration to
25C +/- 2C
Select the appropriately sized vessel/container for alkalinity titrations to
keep the air space above the solution to a minimum. Minimizing the air space above the sample reduces the absorption of CO2 from the atmosphere.
The standard titrant for US EPA Method 310.1 (Alkalinity) is
0.02 N H2SO4 or HCl for alkalinity concentrations <1000mg CaCO3/L
The potentiometric endpoint for total alkalinity is a pH of
Alkalinity is the measure of the
capacity to neutralize acids
Bromcresol green, methyl red and metacresol purple indicators are used in what test?
Compared to a solution with a pH of 4, an acid solution with a pH of 2 is
100 times as acidic
What type of sample should be collected for pH testing?
A grab sample
In the acidity titration method, phenolphthalein is used in the process of titration as a(n)
If a sample of water is known to be basic, which buffers should be used to standardize the pH meter before pH measurement?
7 and 10
A sample has a pH of 6.5 at 25C. This sample can be said to be
The pHs of six grab samples are 6.0, 7.5,6.9,5.2, 8.9, and 8.5. from this, we may conclude that the pH of the composite sample is
pH values cannot be averaged. It cannot be determined from the data given because standard units cannot be averaged.
In the titration method for alkalinity, the acid titrant is standardized with which solution?
Sodium carbonate (Na2CO3)
The definition of pH is
the negative logarithm of the hydrogen ion activity
Acidity in wastewater can be caused by
Septic anaerobic conditions in the collection system
What three principle forms of alkalinity are present in many waters?
Carbonate, hydroxide, and bicarbonate
When no phenolphthalein alkalinity is found in a wastewater sample, all of the remaining alkalinity present is
What has the strongest effect on a pH measurement
How many buffers are recommended for proper calibration of a pH meter?
How often should a pH meter be calibrated to ensure accuracy?
Which parameter is responsible for changing the slope of a pH meter calibration?
The concentration of hydrogen ions is most closely related to
The pH endpoint for a total alkalinity test is
Why is it important to identify materials which will contribute hardness to water
Customers complain about hard water
What are some common methods of water softening?
lime, soda-ash/sodium carbonate, ion exchange
Why is it important to know the alkalinity of your water?
it is an important factor in coagulation, flocculation and corrosion control.
Alkalinity can prevent water from becoming acidic and corrosive
Titrant for alkalinity
Titrant for hardness
0.01 M EDTA
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