CWEA LABORATORY ANALYST GRADE 2 EXAM
1. Which of the following is the primary purpose of quality
assurance in a wastewater laboratory?
A. To reduce staffing requirements
B. To increase sample holding times
C. To ensure reliable and defensible analytical results
D. To eliminate all laboratory documentation
Rationale: Quality assurance (QA) programs are designed to
ensure that laboratory data are accurate, precise, reproducible,
and legally defensible. QA includes procedures such as
calibration, documentation, training, and audits to maintain
confidence in analytical results.
2. What is the correct unit commonly used to report
biochemical oxygen demand (BOD)?
A. mg/L
B. mg/L O₂
C. ppm chlorine
D. NTU
Rationale: BOD measures the amount of dissolved oxygen
consumed by microorganisms during decomposition of organic
matter. It is reported as milligrams of oxygen per liter (mg/L
O₂).
3. Which piece of laboratory equipment is primarily used to
measure pH?
A. Spectrophotometer
B. Turbidimeter
,C. pH meter
D. Conductivity probe
Rationale: A pH meter measures hydrogen ion activity in a
solution and provides accurate pH readings. Proper calibration
with buffer solutions is essential before use.
4. Which safety document contains information regarding
chemical hazards and handling procedures?
A. Chain of Custody
B. SOP Manual
C. Calibration Log
D. Safety Data Sheet (SDS)
Rationale: Safety Data Sheets provide critical information about
chemical hazards, safe handling, storage, exposure limits, and
emergency procedures required by OSHA regulations.
5. What is the acceptable temperature range for storing
most microbiological water samples before analysis?
A. 15–20°C
B. 25–30°C
C. ≤6°C without freezing
D. 35–40°C
Rationale: Most microbiological samples must be cooled to 6°C
or below to minimize biological activity and preserve sample
integrity without freezing the organisms.
6. Which analytical method is commonly used to determine
turbidity?
,A. Gravimetric analysis
B. Titration
C. Nephelometric measurement
D. Gas chromatography
Rationale: Turbidity is commonly measured using nephelometric
methods, which quantify light scattered by suspended particles
in water.
7. In laboratory terminology, accuracy refers to:
A. Reproducibility of results
B. Number of analyses completed
C. Closeness of a measurement to the true value
D. Consistency among analysts
Rationale: Accuracy describes how close a measured result is to
the actual or accepted value, whereas precision refers to
repeatability.
8. What is the primary purpose of a laboratory blank?
A. To calibrate equipment
B. To detect contamination introduced during analysis
C. To increase sample concentration
D. To verify sample preservation
Rationale: Laboratory blanks contain no analyte and are
analyzed to determine whether contamination occurred from
reagents, glassware, or handling procedures.
9. Which of the following is a common preservative for
metals analysis?
, A. Sodium hydroxide
B. Potassium chloride
C. Nitric acid
D. Sulfur powder
Rationale: Nitric acid is commonly added to metals samples to
lower pH and prevent metals from precipitating or adsorbing to
container walls.
10. What does TSS stand for in wastewater analysis?
A. Total Soluble Salts
B. Total Suspended Solids
C. Total Sample Stability
D. Total Settling Solids
Rationale: TSS measures the concentration of suspended
particles retained on a filter and is an important indicator of
wastewater quality.
11. Which type of titration is commonly used to
determine alkalinity?
A. Redox titration
B. Complexometric titration
C. Acid-base titration
D. Precipitation titration
Rationale: Alkalinity is measured by titrating the sample with a
standardized acid to specific pH endpoints.
12. What is the function of a calibration curve in
instrumental analysis?
1. Which of the following is the primary purpose of quality
assurance in a wastewater laboratory?
A. To reduce staffing requirements
B. To increase sample holding times
C. To ensure reliable and defensible analytical results
D. To eliminate all laboratory documentation
Rationale: Quality assurance (QA) programs are designed to
ensure that laboratory data are accurate, precise, reproducible,
and legally defensible. QA includes procedures such as
calibration, documentation, training, and audits to maintain
confidence in analytical results.
2. What is the correct unit commonly used to report
biochemical oxygen demand (BOD)?
A. mg/L
B. mg/L O₂
C. ppm chlorine
D. NTU
Rationale: BOD measures the amount of dissolved oxygen
consumed by microorganisms during decomposition of organic
matter. It is reported as milligrams of oxygen per liter (mg/L
O₂).
3. Which piece of laboratory equipment is primarily used to
measure pH?
A. Spectrophotometer
B. Turbidimeter
,C. pH meter
D. Conductivity probe
Rationale: A pH meter measures hydrogen ion activity in a
solution and provides accurate pH readings. Proper calibration
with buffer solutions is essential before use.
4. Which safety document contains information regarding
chemical hazards and handling procedures?
A. Chain of Custody
B. SOP Manual
C. Calibration Log
D. Safety Data Sheet (SDS)
Rationale: Safety Data Sheets provide critical information about
chemical hazards, safe handling, storage, exposure limits, and
emergency procedures required by OSHA regulations.
5. What is the acceptable temperature range for storing
most microbiological water samples before analysis?
A. 15–20°C
B. 25–30°C
C. ≤6°C without freezing
D. 35–40°C
Rationale: Most microbiological samples must be cooled to 6°C
or below to minimize biological activity and preserve sample
integrity without freezing the organisms.
6. Which analytical method is commonly used to determine
turbidity?
,A. Gravimetric analysis
B. Titration
C. Nephelometric measurement
D. Gas chromatography
Rationale: Turbidity is commonly measured using nephelometric
methods, which quantify light scattered by suspended particles
in water.
7. In laboratory terminology, accuracy refers to:
A. Reproducibility of results
B. Number of analyses completed
C. Closeness of a measurement to the true value
D. Consistency among analysts
Rationale: Accuracy describes how close a measured result is to
the actual or accepted value, whereas precision refers to
repeatability.
8. What is the primary purpose of a laboratory blank?
A. To calibrate equipment
B. To detect contamination introduced during analysis
C. To increase sample concentration
D. To verify sample preservation
Rationale: Laboratory blanks contain no analyte and are
analyzed to determine whether contamination occurred from
reagents, glassware, or handling procedures.
9. Which of the following is a common preservative for
metals analysis?
, A. Sodium hydroxide
B. Potassium chloride
C. Nitric acid
D. Sulfur powder
Rationale: Nitric acid is commonly added to metals samples to
lower pH and prevent metals from precipitating or adsorbing to
container walls.
10. What does TSS stand for in wastewater analysis?
A. Total Soluble Salts
B. Total Suspended Solids
C. Total Sample Stability
D. Total Settling Solids
Rationale: TSS measures the concentration of suspended
particles retained on a filter and is an important indicator of
wastewater quality.
11. Which type of titration is commonly used to
determine alkalinity?
A. Redox titration
B. Complexometric titration
C. Acid-base titration
D. Precipitation titration
Rationale: Alkalinity is measured by titrating the sample with a
standardized acid to specific pH endpoints.
12. What is the function of a calibration curve in
instrumental analysis?
