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CWEA Laboratory Analyst Grade 1 Certification
Exam QUESTIONS AND DETAILED SOLUTIONS JUST
RELEASED
CWEA Laboratory Analyst Grade 1 Certification Exam
Practice Questions with Answers and Rationales
10 POINT EXAM COVERAGE AREAS (MOST TESTED)
1. Microbiological Methods - Coliform fermentation technique (presumptive, confirmed,
completed phases), Heterotrophic Plate Count (HPC), enzyme substrate tests, MPN
determination, sterile technique, media preparation
2. Solids Analysis - Total Solids (TS), Total Suspended Solids (TSS), Total Dissolved Solids (TDS),
volatile solids, constant weight determination, drying oven temperatures (103-105°C, 180°C,
550°C)
3. Biochemical Oxygen Demand (BOD) - BOD procedure, sample preparation, pH adjustment,
dechlorination, seeding, dissolved oxygen measurement, incubation at 20°C for 5 days
4. Chemical & Physical Analyses - Chloride (argentometric and mercuric nitrate methods),
alkalinity, hardness (EDTA titration), conductivity, pH, turbidity, color (true vs. apparent)
5. Sampling & Sample Preservation - Grab vs. composite samples, sample labels, chain of custody,
preservation requirements (e.g., BOD 48 hours, pH 15 minutes), sample holding times
6. Laboratory Safety & Quality Assurance - Laboratory safety, chemical hygiene, electrical fire
response, QA/QC concepts (precision, accuracy, bias), analytical balance types, glassware
selection
7. Regulatory & Professional Standards - Minimum qualifications for certification (22 CCR §
64812.00), CWEA LAB certification grades and their required testing methods
8. Calculations & Unit Conversions - Concentration units (mg/L), normality equation (N₁V₁ = N₂V₂),
temperature conversion, significant figures, rounding rules
Question 1: For the Heterotrophic Plate Count (HPC) analysis, the media water bath must be maintained
at which temperature and for what duration?
A) 35°C for 2 hours
B) 45°C for 3 hours
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C) 55°C for 4 hours
D) 40°C for 1 hour
Correct Answer: B
Rationale: HPC media must be maintained in a 45°C water bath for 3 hours to keep the agar molten and
ready for pour plating without harming the microorganisms .
Question 2: What is the correct formula for converting Fahrenheit to Celsius?
A) C = (F + 32) × 5/9
B) C = (F − 32) × 5/9
C) C = (F − 32) × 9/5
D) C = (F × 9/5) + 32
Correct Answer: B
Rationale: The formula for converting Fahrenheit to Celsius is (F−32)×5/9. For example, 212°F = 100°C .
Question 3: Precision in laboratory analysis is best defined as:
A) How close a measurement is to the true value
B) A measure of how close a series of measurements are to one another
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C) Consistent deviation from the true value
D) The combination of bias and precision
Correct Answer: B
Rationale: Precision measures the degree of agreement among replicate analyses of a sample, usually
expressed as the standard deviation .
Question 4: Accuracy in laboratory analysis is best defined as:
A) How close a series of measurements are to one another
B) Consistent deviation from the true value
C) How close a measurement is to the true value
D) A measure of random error
Correct Answer: C
Rationale: Accuracy is the combination of bias and precision of an analytical procedure, reflecting the
closeness of a measured value to a true value .
Question 5: The constant weight for total solids analysis is achieved when the weight change is:
A) Less than 1% of previous weight or 0.2 mg
B) Less than 4% of previous weight or 0.5 mg
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C) Less than 10% of previous weight or 1.0 mg
D) Less than 2% of previous weight or 0.3 mg
Correct Answer: B
Rationale: Constant weight for total solids is achieved when the weight change is less than 4% of the
previous weight or 0.5 mg .
Question 6: Total Suspended Solids (TSS) are determined by filtering a well-mixed sample through which
type of filter?
A) Cellulose membrane filter
B) Standard glass fiber filter
C) Nylon mesh filter
D) Silver membrane filter
Correct Answer: B
Rationale: TSS is determined by filtering a well-mixed sample through a weighed standard glass fiber
filter; the residue retained is dried to constant weight at 103-105°C .
Question 7: The analysis of Total Dissolved Solids (TDS) requires the filtrate to be evaporated to dryness
and dried to constant weight at what temperature?
CWEA Laboratory Analyst Grade 1 Certification
Exam QUESTIONS AND DETAILED SOLUTIONS JUST
RELEASED
CWEA Laboratory Analyst Grade 1 Certification Exam
Practice Questions with Answers and Rationales
10 POINT EXAM COVERAGE AREAS (MOST TESTED)
1. Microbiological Methods - Coliform fermentation technique (presumptive, confirmed,
completed phases), Heterotrophic Plate Count (HPC), enzyme substrate tests, MPN
determination, sterile technique, media preparation
2. Solids Analysis - Total Solids (TS), Total Suspended Solids (TSS), Total Dissolved Solids (TDS),
volatile solids, constant weight determination, drying oven temperatures (103-105°C, 180°C,
550°C)
3. Biochemical Oxygen Demand (BOD) - BOD procedure, sample preparation, pH adjustment,
dechlorination, seeding, dissolved oxygen measurement, incubation at 20°C for 5 days
4. Chemical & Physical Analyses - Chloride (argentometric and mercuric nitrate methods),
alkalinity, hardness (EDTA titration), conductivity, pH, turbidity, color (true vs. apparent)
5. Sampling & Sample Preservation - Grab vs. composite samples, sample labels, chain of custody,
preservation requirements (e.g., BOD 48 hours, pH 15 minutes), sample holding times
6. Laboratory Safety & Quality Assurance - Laboratory safety, chemical hygiene, electrical fire
response, QA/QC concepts (precision, accuracy, bias), analytical balance types, glassware
selection
7. Regulatory & Professional Standards - Minimum qualifications for certification (22 CCR §
64812.00), CWEA LAB certification grades and their required testing methods
8. Calculations & Unit Conversions - Concentration units (mg/L), normality equation (N₁V₁ = N₂V₂),
temperature conversion, significant figures, rounding rules
Question 1: For the Heterotrophic Plate Count (HPC) analysis, the media water bath must be maintained
at which temperature and for what duration?
A) 35°C for 2 hours
B) 45°C for 3 hours
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C) 55°C for 4 hours
D) 40°C for 1 hour
Correct Answer: B
Rationale: HPC media must be maintained in a 45°C water bath for 3 hours to keep the agar molten and
ready for pour plating without harming the microorganisms .
Question 2: What is the correct formula for converting Fahrenheit to Celsius?
A) C = (F + 32) × 5/9
B) C = (F − 32) × 5/9
C) C = (F − 32) × 9/5
D) C = (F × 9/5) + 32
Correct Answer: B
Rationale: The formula for converting Fahrenheit to Celsius is (F−32)×5/9. For example, 212°F = 100°C .
Question 3: Precision in laboratory analysis is best defined as:
A) How close a measurement is to the true value
B) A measure of how close a series of measurements are to one another
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C) Consistent deviation from the true value
D) The combination of bias and precision
Correct Answer: B
Rationale: Precision measures the degree of agreement among replicate analyses of a sample, usually
expressed as the standard deviation .
Question 4: Accuracy in laboratory analysis is best defined as:
A) How close a series of measurements are to one another
B) Consistent deviation from the true value
C) How close a measurement is to the true value
D) A measure of random error
Correct Answer: C
Rationale: Accuracy is the combination of bias and precision of an analytical procedure, reflecting the
closeness of a measured value to a true value .
Question 5: The constant weight for total solids analysis is achieved when the weight change is:
A) Less than 1% of previous weight or 0.2 mg
B) Less than 4% of previous weight or 0.5 mg
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C) Less than 10% of previous weight or 1.0 mg
D) Less than 2% of previous weight or 0.3 mg
Correct Answer: B
Rationale: Constant weight for total solids is achieved when the weight change is less than 4% of the
previous weight or 0.5 mg .
Question 6: Total Suspended Solids (TSS) are determined by filtering a well-mixed sample through which
type of filter?
A) Cellulose membrane filter
B) Standard glass fiber filter
C) Nylon mesh filter
D) Silver membrane filter
Correct Answer: B
Rationale: TSS is determined by filtering a well-mixed sample through a weighed standard glass fiber
filter; the residue retained is dried to constant weight at 103-105°C .
Question 7: The analysis of Total Dissolved Solids (TDS) requires the filtrate to be evaporated to dryness
and dried to constant weight at what temperature?
