Laboratory Practice Flashcards
7 cards from real STP practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Laboratory Practice flashcards as text
A scientist needs to prepare a 100 mM NaCl solution. If the molecular weight of NaCl is 58.44 g/mol, how many grams are needed to make 500 mL of this solution?
Answer: 2.922 g
Moles needed = 0.1 mol/L × 0.5 L = 0.05 mol; mass = 0.05 mol × 58.44 g/mol = 2.922 g.
Which of the following is the correct hierarchy of controls for managing laboratory hazards, from most to least preferred?
Answer: Elimination → Substitution → Engineering controls → Administrative controls → PPE
The hierarchy of controls prioritizes eliminating the hazard first, then substitution, engineering controls, administrative controls, and lastly PPE as the least reliable protection.
In a double-blind clinical trial, which of the following BEST describes the role of laboratory staff processing samples?
Answer: Laboratory staff should be blinded to sample group assignment to prevent bias in processing or analysis
In a double-blind study, laboratory personnel are also blinded to treatment assignments to prevent conscious or unconscious bias in sample handling and result interpretation.
What does the term 'limit of detection' (LOD) mean in analytical chemistry?
Answer: The lowest quantity of an analyte that can be distinguished from background with statistical confidence
The LOD is the smallest amount of analyte that produces a signal distinguishable from background noise, typically defined as signal-to-noise ratio of 3:1.
A researcher is working with a Category B infectious substance for shipping. Under US DOT regulations, which packaging specification must be used?
Answer: P650 packaging specification for UN3373
Category B infectious substances classified as UN3373 must be shipped using P650 packaging, which requires primary, secondary, and outer containers meeting specific requirements.
Which statistical term describes the closeness of agreement between independent test results obtained under the same conditions (same operator, same equipment, short time interval)?
Answer: Repeatability
Repeatability (intra-assay precision) measures agreement between results obtained by the same analyst using the same equipment in a short timeframe; reproducibility applies across different conditions.
When storing flammable solvents in a laboratory, which practice is REQUIRED for safety?
Answer: Keeping all flammable liquids in an approved flammable storage cabinet away from ignition sources
Flammable liquids must be stored in approved flammable storage cabinets designed to contain vapors and withstand fire, away from ignition sources.