10 exam-style questions with answers and explanations, straight from our 1,030-question bank. Tap an answer to check yourself. When you're ready, take the scored version in the free practice test.
These 10 free RELT questions are organized by exam domain, so you can see how each part of the Registered Environmental Laboratory Technologist blueprint is tested. Reveal the answer and explanation under each question.
For a dissolved-lead determination under 40 CFR Part 136, a collector acidifies an unfiltered, visibly turbid water sample to pH below 2. The laboratory filters it the following day and obtains acceptable calibration and recovery checks. How should the reviewer characterize what was measured?
Correct answer: A - It may include originally particle-bound lead released by the acid.
Nitric acid splashes into a technologist’s eye during sample preservation. An emergency eyewash is immediately accessible, and a coworker is present. Which response takes priority?
Correct answer: B - Immediately flush the eye at the eyewash while the coworker calls for help.
Two 100 mL water samples both have pH 7.8 at the same temperature. After the same small addition of strong acid, one falls to pH 5.4 while the other remains at pH 7.6. The electrode checks pass. Which measurement would most directly characterize the difference in their resistance to acid addition?
Correct answer: C - Total alkalinity by acid titration.
A seeded five-day biochemical oxygen demand (BOD5) test uses 300 mL bottles. Initial and final dissolved oxygen (DO), in mg/L, are: 3 mL sample: 8.0 initially, 7.1 finally. 15 mL sample: 8.1 initially, 4.1 finally. 60 mL sample: 8.0 initially, 0.4 finally. The seed correction is 0.30 mg/L in each bottle. Use only a dilution with at least 2.0 mg/L DO depletion and at least 1.0 mg/L final DO; other controls are acceptable. Which seed-corrected BOD5 value follows from the qualifying dilution?
Correct answer: D - 74 mg/L, calculated from the 15 mL aliquot.
During GC/MS review, a peak appears 0.03 minute from the target compound’s reference retention time. The laboratory’s identification procedure allows a difference of 0.05 minute and requires a qualifier-to-quantitation ion ratio of 0.45-0.65. The peak’s ratio is 0.18. Calibration, tuning, and the reference spectrum checks pass. What identification is supported?
Correct answer: D - The retention-time criterion is met, but the target compound is not confirmed.
High-chloride groundwater gives an unexpectedly large arsenic signal at mass-to-charge ratio 75 by ICP-MS. An arsenic-free chloride interference-check solution produces a similar signal, while alternating acid blanks are clean and a low-chloride arsenic control passes. Which mechanism best explains this pattern?
Correct answer: D - Overlap from an argon-chloride ion at mass 75.
At 09:00, a supervisor has one available technologist; a second analysis cannot be started before 09:45. All four waiting samples are properly preserved. Their verified holding-time deadlines are 09:30 for E. coli, 14:00 for BOD5, 17:00 for total suspended solids, and seven days later for chemical oxygen demand (COD). The COD client has requested results by 10:00. What should be assigned first?
Correct answer: A - Begin the E. coli setup; its incubation deadline is closest.
A groundwater project must determine whether a contaminant is below 2.0 µg/L. Matrix-related dilution raises the sample-specific reporting limit to 8.0 µg/L, and the final result is reported as “not detected, <8.0 µg/L.” The clean-water method detection limit is 0.20 µg/L. How does this result address the project’s decision?
Correct answer: B - The available result cannot resolve the 2.0 µg/L decision.
A reuse decision must be made separately for each of twelve soil stockpiles. The proposed sampling plan takes representative increments within every stockpile, then combines equal masses from all twelve into one composite for metals analysis. The laboratory can measure that composite with excellent precision. Which revision preserves the decision the project actually needs?
Correct answer: A - Keep each stockpile’s representative composite separate for analysis.
An extraction batch has a clean method blank and 98% recovery in the laboratory control sample. One wastewater sample gives matrix-spike and matrix-spike-duplicate recoveries of 44% and 47%; its native analyte concentration is negligible relative to the spike. The applicable recovery range is 75-125%. Spike additions and calculations have been verified, and the other samples have acceptable quality controls. Where should the investigation focus first?
Correct answer: C - Poor recovery associated with the wastewater matrix.
The full bank has 1,020 more RELT questions with explanations.
Continue in the free practice test →
View plans