Laboratory Equipment & Techniques Flashcards
7 cards from real MLS 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 Equipment & Techniques flashcards as text
Which class of fire extinguisher should be used for a burning electrical equipment fire in the laboratory?
Answer: Class C
Class C extinguishers use non-conductive agents (CO2 or dry chemical) suitable for electrical fires where water-based agents would be dangerous.
When using a refractometer to measure urine specific gravity, the instrument measures:
Answer: The refractive index, which correlates with solute concentration
A refractometer measures how much light bends (refractive index) as it passes through the sample, which correlates with dissolved solute concentration and specific gravity.
Which of the following describes the correct procedure when using a swinging-bucket rotor centrifuge for density gradient separations?
Answer: Balance opposing tubes to within manufacturer tolerances before spinning
Proper balancing of opposing buckets is essential to prevent rotor damage, instrument vibration, and potential centrifuge failure.
An autoclave that sterilizes at 121°C for 15 minutes uses which combination of conditions?
Answer: Moist heat (steam) at 15 psi
Standard autoclaving uses saturated steam (moist heat) at 15 psi (103 kPa) above atmospheric pressure, achieving 121°C for effective sterilization.
A laboratory balance displays 5.003 g when weighing a 5.000 g reference weight. The balance is:
Answer: Precise but not accurate
If the balance consistently reads 5.003 g (reproducible), it is precise; however, since it deviates from the true 5.000 g value, it is not accurate.
Which microscopy technique uses oblique illumination to produce a three-dimensional appearance without staining, making it ideal for viewing unstained wet preparations?
Answer: Phase contrast microscopy
Phase contrast microscopy converts phase shifts in light passing through transparent specimens into visible brightness changes, allowing visualization of unstained cells.
What is the primary purpose of a HEPA filter in a biological safety cabinet?
Answer: To trap particulates ≥0.3 µm with ≥99.97% efficiency
HEPA (High Efficiency Particulate Air) filters remove at least 99.97% of airborne particles ≥0.3 µm in diameter, protecting against biological aerosols.