CWEA Grade 1 Laboratory Analyst Exam Prep Practice Questions &
Answers 2 versions
This specialized technical preparation resource features a comprehensive practice
question bank of targeted items and verified answers tailored to the California Water
Environment Association (CWEA) Grade 1 Laboratory Analyst certification exam. It
delivers deep-dive coverage of introductory wastewater laboratory procedures, including
sample collection, quality assurance (QA/QC) tracking, biochemical oxygen demand
(BOD) testing, pH monitoring, and basic mathematical laboratory calculations.
Laboratory technicians and environmental specialists will master critical safety
parameters, standard methods compliance, and EPA clean water standards to ensure a
passing score on their proctored evaluation.
1. What is the first step when calibrating a pH meter?
A) Rinse the electrode with deionized water
B) Allow the electrode to warm up and stabilize
C) Place the electrode in pH 7 buffer
D) Adjust the slope control
Rationale: The pH meter and electrode must be allowed to stabilize at room temperature
before calibration begins.
2. What is the purpose of a nitrification inhibitor in BOD analysis?
A) To kill all bacteria
B) To prevent oxidation of ammonia by nitrifying bacteria
C) To increase oxygen consumption
D) To adjust pH
Rationale: Nitrification inhibitors prevent ammonia-oxidizing bacteria from consuming
oxygen, ensuring BOD measures only carbonaceous demand.
,3. What is the holding time for a nitrate sample?
A) 6 hours
B) 48 hours
C) 24 hours
D) 7 days
Rationale: Nitrate samples must be analyzed within 48 hours when preserved at 4°C.
4. What is the correct way to store a glass fiber filter for TSS?
A) In a desiccator at room temperature
B) In a desiccator after drying at 103–105°C
C) In a refrigerator
D) In a freezer
Rationale: Filters must be dried and cooled in a desiccator to prevent moisture absorption
before weighing.
5. What is the formula for calculating % recovery in a matrix spike?
A) (Spike added / Spike found) × 100
B) ((Spike found - Sample result) / Spike added) × 100
C) (Sample result / Spike added) × 100
D) (Spike found / Sample result) × 100
Rationale: Percent recovery = ((spike found - sample result) / spike added) × 100.
6. What is the acceptable RPD for duplicate samples?
A) 5%
B) 20%
C) 50%
D) 100%
,Rationale: Relative percent difference (RPD) for duplicates should generally be less than
20% for acceptable precision.
7. What is the purpose of a field duplicate?
A) To calibrate the instrument
B) To assess precision of sampling and analysis
C) To measure pH
D) To determine holding time
Rationale: Field duplicates evaluate precision from both sampling and laboratory analysis.
8. What is the difference between a method blank and a reagent blank?
A) Method blank includes sample matrix; reagent blank does not
B) Method blank goes through entire analytical procedure; reagent blank does not
C) Reagent blank includes sample matrix
D) There is no difference
Rationale: A method blank is carried through all preparation and analysis steps; a reagent
blank only tests the reagents.
9. What is the proper procedure for cleaning glassware for trace metals analysis?
A) Rinse with tap water only
B) Wash with detergent, rinse with tap water, then acid rinse with 1:1 HNO3
C) Rinse with deionized water only
D) Wash with soap and dry with a towel
Rationale: Acid rinsing removes metal contamination from glassware surfaces.
, 10. What is the purpose of a control chart?
A) To track sample volume
B) To monitor analytical performance over time
C) To calibrate instruments
D) To schedule maintenance
Rationale: Control charts detect trends, shifts, and out-of-control situations in analytical
results.
11. How often should a laboratory balance be calibrated?
A) Monthly
B) Daily or before each use with certified weights
C) Yearly
D) Only when new
Rationale: Balances should be checked daily with certified weights to ensure accuracy.
12. What is the correct technique for pipetting viscous liquids?
A) Use a serological pipette and blow out
B) Use a positive displacement pipette and allow drainage
C) Use a volumetric pipette and blow out
D) Use a Pasteur pipette
Rationale: Positive displacement pipettes are designed for viscous liquids and volatile
solvents.
13. What is the proper way to read a meniscus?
A) Read the top of the meniscus
B) Read the bottom of the meniscus at eye level
C) Read from above
D) Read from below
Answers 2 versions
This specialized technical preparation resource features a comprehensive practice
question bank of targeted items and verified answers tailored to the California Water
Environment Association (CWEA) Grade 1 Laboratory Analyst certification exam. It
delivers deep-dive coverage of introductory wastewater laboratory procedures, including
sample collection, quality assurance (QA/QC) tracking, biochemical oxygen demand
(BOD) testing, pH monitoring, and basic mathematical laboratory calculations.
Laboratory technicians and environmental specialists will master critical safety
parameters, standard methods compliance, and EPA clean water standards to ensure a
passing score on their proctored evaluation.
1. What is the first step when calibrating a pH meter?
A) Rinse the electrode with deionized water
B) Allow the electrode to warm up and stabilize
C) Place the electrode in pH 7 buffer
D) Adjust the slope control
Rationale: The pH meter and electrode must be allowed to stabilize at room temperature
before calibration begins.
2. What is the purpose of a nitrification inhibitor in BOD analysis?
A) To kill all bacteria
B) To prevent oxidation of ammonia by nitrifying bacteria
C) To increase oxygen consumption
D) To adjust pH
Rationale: Nitrification inhibitors prevent ammonia-oxidizing bacteria from consuming
oxygen, ensuring BOD measures only carbonaceous demand.
,3. What is the holding time for a nitrate sample?
A) 6 hours
B) 48 hours
C) 24 hours
D) 7 days
Rationale: Nitrate samples must be analyzed within 48 hours when preserved at 4°C.
4. What is the correct way to store a glass fiber filter for TSS?
A) In a desiccator at room temperature
B) In a desiccator after drying at 103–105°C
C) In a refrigerator
D) In a freezer
Rationale: Filters must be dried and cooled in a desiccator to prevent moisture absorption
before weighing.
5. What is the formula for calculating % recovery in a matrix spike?
A) (Spike added / Spike found) × 100
B) ((Spike found - Sample result) / Spike added) × 100
C) (Sample result / Spike added) × 100
D) (Spike found / Sample result) × 100
Rationale: Percent recovery = ((spike found - sample result) / spike added) × 100.
6. What is the acceptable RPD for duplicate samples?
A) 5%
B) 20%
C) 50%
D) 100%
,Rationale: Relative percent difference (RPD) for duplicates should generally be less than
20% for acceptable precision.
7. What is the purpose of a field duplicate?
A) To calibrate the instrument
B) To assess precision of sampling and analysis
C) To measure pH
D) To determine holding time
Rationale: Field duplicates evaluate precision from both sampling and laboratory analysis.
8. What is the difference between a method blank and a reagent blank?
A) Method blank includes sample matrix; reagent blank does not
B) Method blank goes through entire analytical procedure; reagent blank does not
C) Reagent blank includes sample matrix
D) There is no difference
Rationale: A method blank is carried through all preparation and analysis steps; a reagent
blank only tests the reagents.
9. What is the proper procedure for cleaning glassware for trace metals analysis?
A) Rinse with tap water only
B) Wash with detergent, rinse with tap water, then acid rinse with 1:1 HNO3
C) Rinse with deionized water only
D) Wash with soap and dry with a towel
Rationale: Acid rinsing removes metal contamination from glassware surfaces.
, 10. What is the purpose of a control chart?
A) To track sample volume
B) To monitor analytical performance over time
C) To calibrate instruments
D) To schedule maintenance
Rationale: Control charts detect trends, shifts, and out-of-control situations in analytical
results.
11. How often should a laboratory balance be calibrated?
A) Monthly
B) Daily or before each use with certified weights
C) Yearly
D) Only when new
Rationale: Balances should be checked daily with certified weights to ensure accuracy.
12. What is the correct technique for pipetting viscous liquids?
A) Use a serological pipette and blow out
B) Use a positive displacement pipette and allow drainage
C) Use a volumetric pipette and blow out
D) Use a Pasteur pipette
Rationale: Positive displacement pipettes are designed for viscous liquids and volatile
solvents.
13. What is the proper way to read a meniscus?
A) Read the top of the meniscus
B) Read the bottom of the meniscus at eye level
C) Read from above
D) Read from below
