CWEA GRADE I LABORATORY
ANALYST EXAM/ QUESTIONS &
WELL DETAILED
ANSWERS/GRADE A+ ASSURED
1. Sample pretreatment for BOD - ANSWER assuring that the samples are neutralized to pH range
between 6.5 and 7.5 and any residual chlorine has been de chlorinated
2. BOD determination is an empirical test in which standardized lab procedures are used to -
ANSWER determine the relative oxygen requirements of wastewaters, effluents and polluted
waters
3.
The sample receiving log must record time and date sampled - ANSWER Sample collector, nature of
sample, analyses to be performed, preservatives, condition of sample and sample recipient
4. When preparing diluted calibration standards from a stock standard, use combination of the
following to get the most precise standard - ANSWER Class A volumetric flask and class A
volumetric pipet
5. How is alkalinity measured - ANSWER Titration of a sample with a standard solution of either
sulfuric acid or hydrochloric acid to predetermined pH endpoint
6.
Total Dissolved Solids - ANSWER A well mixed sample is filtered through standard glass fiber filter
and filtrate is evaporated to dryness in weighed dish and dried to constant weight at 180 degrees C
7.
Chloride - ANSWER - Major anion found in many natural waters
, - Can impart salty taste in H2O
8. What increases concentration of chloride in wastewater - ANSWER Chloride in human diet and
softeners flushed into sanitary sewer system
9. 2 most prevalent methods of measuring chloride - ANSWER argentometric and mercuric nitrate
10. Argentometric - ANSWER Titration of sample with standard solution of silver nitrate (AgNO3)
- Indicator: Chromate ions (CrO4)
- End point: reddish silver chromate
11. Mercuric Nitrate - ANSWER Titration with standard mercuric nitrate solution
12. -pH must be adjusted between 2.3 and 2.8
- Indicator: Diphenyl carbazone
- End point: Change from blue to purple in presence of mercury
13. Interference of Mercuric Nitrate Method - ANSWER Sulfide, bromide, orthophosphate (over 30
ppm), and iodide
14. Why does color change in water - ANSWER Presence of decaying vegetable matter, metal ions
(ie. iron) or industrial and domestic pollution
15. How is color measured - ANSWER Measured using visual comparison method
16. Visual comparison method - ANSWER Sample compared to standards using matched nessler
tubes
- Standards prepared with solution containing cholorplatinate and cobaltous chloride
17. Standard units for color - ANSWER One unit= color resulting from 1 mg of platinum/L
18. 2 color reporting - ANSWER True and Apparent
, 19. True color - ANSWER Color from dissolved substances, determine using sample treated to
remove turbidity
20. Apparent Color - ANSWER Includes dissolved and suspended solids
21. Conductivity - ANSWER H2Os capability to pass electrical flow
22. Conductivity of pure water - ANSWER 0
23. Units of conductivity - ANSWER micromhos/cm
24. Temperature conductivity should be read at - ANSWER 25 degrees Celcius
25. How is conductivity affected - ANSWER Mobility of ions, conductivity is dependent on viscosity
26. Viscosity - ANSWER A liquids ability to resist flow, higher the viscosity the lower the flow
27. Relationship of temperature and viscosity - ANSWER Inverse
28. Acid - ANSWER A compound which liberates hydrogen ions and has a pH below 7.
29. Alkalinity: - ANSWER The measurement of a sample's capacity to neutralize acid.
30. Alkalinity measures - ANSWER The carbonate, bicarbonate, and hydroxide ion concentration
found in water
31. Primary reason for measuring alkalinity - ANSWER Used in control of many water and
wastewater unit processes
32. The phenolphthalein alkalinity of a water sample is zero if: - ANSWER The pH is greater than 8.3
ANALYST EXAM/ QUESTIONS &
WELL DETAILED
ANSWERS/GRADE A+ ASSURED
1. Sample pretreatment for BOD - ANSWER assuring that the samples are neutralized to pH range
between 6.5 and 7.5 and any residual chlorine has been de chlorinated
2. BOD determination is an empirical test in which standardized lab procedures are used to -
ANSWER determine the relative oxygen requirements of wastewaters, effluents and polluted
waters
3.
The sample receiving log must record time and date sampled - ANSWER Sample collector, nature of
sample, analyses to be performed, preservatives, condition of sample and sample recipient
4. When preparing diluted calibration standards from a stock standard, use combination of the
following to get the most precise standard - ANSWER Class A volumetric flask and class A
volumetric pipet
5. How is alkalinity measured - ANSWER Titration of a sample with a standard solution of either
sulfuric acid or hydrochloric acid to predetermined pH endpoint
6.
Total Dissolved Solids - ANSWER A well mixed sample is filtered through standard glass fiber filter
and filtrate is evaporated to dryness in weighed dish and dried to constant weight at 180 degrees C
7.
Chloride - ANSWER - Major anion found in many natural waters
, - Can impart salty taste in H2O
8. What increases concentration of chloride in wastewater - ANSWER Chloride in human diet and
softeners flushed into sanitary sewer system
9. 2 most prevalent methods of measuring chloride - ANSWER argentometric and mercuric nitrate
10. Argentometric - ANSWER Titration of sample with standard solution of silver nitrate (AgNO3)
- Indicator: Chromate ions (CrO4)
- End point: reddish silver chromate
11. Mercuric Nitrate - ANSWER Titration with standard mercuric nitrate solution
12. -pH must be adjusted between 2.3 and 2.8
- Indicator: Diphenyl carbazone
- End point: Change from blue to purple in presence of mercury
13. Interference of Mercuric Nitrate Method - ANSWER Sulfide, bromide, orthophosphate (over 30
ppm), and iodide
14. Why does color change in water - ANSWER Presence of decaying vegetable matter, metal ions
(ie. iron) or industrial and domestic pollution
15. How is color measured - ANSWER Measured using visual comparison method
16. Visual comparison method - ANSWER Sample compared to standards using matched nessler
tubes
- Standards prepared with solution containing cholorplatinate and cobaltous chloride
17. Standard units for color - ANSWER One unit= color resulting from 1 mg of platinum/L
18. 2 color reporting - ANSWER True and Apparent
, 19. True color - ANSWER Color from dissolved substances, determine using sample treated to
remove turbidity
20. Apparent Color - ANSWER Includes dissolved and suspended solids
21. Conductivity - ANSWER H2Os capability to pass electrical flow
22. Conductivity of pure water - ANSWER 0
23. Units of conductivity - ANSWER micromhos/cm
24. Temperature conductivity should be read at - ANSWER 25 degrees Celcius
25. How is conductivity affected - ANSWER Mobility of ions, conductivity is dependent on viscosity
26. Viscosity - ANSWER A liquids ability to resist flow, higher the viscosity the lower the flow
27. Relationship of temperature and viscosity - ANSWER Inverse
28. Acid - ANSWER A compound which liberates hydrogen ions and has a pH below 7.
29. Alkalinity: - ANSWER The measurement of a sample's capacity to neutralize acid.
30. Alkalinity measures - ANSWER The carbonate, bicarbonate, and hydroxide ion concentration
found in water
31. Primary reason for measuring alkalinity - ANSWER Used in control of many water and
wastewater unit processes
32. The phenolphthalein alkalinity of a water sample is zero if: - ANSWER The pH is greater than 8.3
