STP Laboratory Practice 2 — Questions and Answers
Question 1: When a chemical spill occurs on the skin in a laboratory, what is the FIRST action to take?
- Apply a neutralizing agent immediately
- Flush the affected area with large amounts of water for at least 15 minutes (Correct answer)
- Cover the area with a dry cloth
- Notify the supervisor before doing anything
Correct answer: Flush the affected area with large amounts of water for at least 15 minutes
Immediate and prolonged flushing with water dilutes and removes the chemical before it can cause further injury.
Question 2: Which label element is NOT required on a secondary container of a hazardous chemical in a US laboratory under OSHA's Hazard Communication Standard?
- Product identifier
- Hazard warnings
- Manufacturer's full street address (Correct answer)
- Name of the person responsible for the container
Correct answer: Manufacturer's full street address
Secondary container labels require a product identifier and hazard warnings but do not need the manufacturer's full street address.
Question 3: A laboratory worker notices their pipette calibration check is outside the acceptable tolerance range. What should they do?
- Continue using the pipette and note the deviation in the lab notebook
- Remove the pipette from service, label it 'OUT OF SERVICE,' and report it for recalibration (Correct answer)
- Adjust personal technique to compensate for the error
- Use the pipette only for non-critical measurements
Correct answer: Remove the pipette from service, label it 'OUT OF SERVICE,' and report it for recalibration
Equipment outside calibration tolerance must be removed from service to prevent erroneous results and ensure data integrity.
Question 4: What is the purpose of a Material Safety Data Sheet (SDS) Section 8?
- Physical and chemical properties of the substance
- Exposure controls and personal protective equipment requirements (Correct answer)
- Toxicological information and health effects
- First aid measures
Correct answer: Exposure controls and personal protective equipment requirements
SDS Section 8 (Exposure Controls/Personal Protection) specifies occupational exposure limits and required PPE.
Question 5: In a cell culture laboratory, what practice BEST prevents cross-contamination between cell lines?
- Working with multiple cell lines simultaneously to save time
- Changing gloves and decontaminating the hood between handling different cell lines (Correct answer)
- Using the same media bottle for all cell lines to reduce waste
- Keeping all cell lines in the same incubator shelf
Correct answer: Changing gloves and decontaminating the hood between handling different cell lines
Changing gloves and decontaminating surfaces between cell lines prevents transfer of cells, mycoplasma, or other contaminants.
Question 6: Which of the following is the correct disposal method for a broken glass pipette contaminated with a biohazardous material?
- Regular sharps container
- Biohazardous sharps container (Correct answer)
- Regular trash after autoclaving only
- Chemical waste container
Correct answer: Biohazardous sharps container
Sharp objects contaminated with biohazardous materials must go into a biohazardous sharps container to address both the puncture risk and biological hazard.
Question 7: A scientist is setting up a PCR experiment and finds that the positive control failed to amplify. What does this indicate?
- The experimental samples are negative for the target
- There is likely a problem with the PCR reagents, thermal cycler, or protocol (Correct answer)
- The experiment was successful and all samples are truly negative
- The primers are too specific for the target sequence
Correct answer: There is likely a problem with the PCR reagents, thermal cycler, or protocol
A failed positive control indicates a technical failure in the assay itself, meaning results from the experimental samples cannot be interpreted.
STP Laboratory Practice 2
When a chemical spill occurs on the skin in a laboratory, what is the FIRST action to take?