STP Laboratory Practice 5

Question 1

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?

Accepted Answer

2.922 g

Answer

Moles needed = 0.1 mol/L × 0.5 L = 0.05 mol; mass = 0.05 mol × 58.44 g/mol = 2.922 g.

Question 2

Which of the following is the correct hierarchy of controls for managing laboratory hazards, from most to least preferred?

Accepted Answer

Elimination → Substitution → Engineering controls → Administrative controls → PPE

Answer

The hierarchy of controls prioritizes eliminating the hazard first, then substitution, engineering controls, administrative controls, and lastly PPE as the least reliable protection.

Question 3

In a double-blind clinical trial, which of the following BEST describes the role of laboratory staff processing samples?

Accepted Answer

Laboratory staff should be blinded to sample group assignment to prevent bias in processing or analysis

Answer

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.

Question 4

What does the term 'limit of detection' (LOD) mean in analytical chemistry?

Accepted Answer

The lowest quantity of an analyte that can be distinguished from background with statistical confidence

Answer

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.

Question 5

A researcher is working with a Category B infectious substance for shipping. Under US DOT regulations, which packaging specification must be used?

Accepted Answer

P650 packaging specification for UN3373

Answer

Category B infectious substances classified as UN3373 must be shipped using P650 packaging, which requires primary, secondary, and outer containers meeting specific requirements.

(STP) Scientist Training Programme Practice Test

(STP) Scientist Training Programme Practice Test

STP Laboratory Practice 5