Chemistry Test Analytical Chemistry 2 — Questions and Answers
Question 1: Which technique separates compounds based on their different rates of migration through a stationary phase under a mobile phase?
- Chromatography (Correct answer)
- Electrophoresis
- Distillation
- Crystallization
Correct answer: Chromatography
Chromatography separates compounds by differential migration between stationary and mobile phases.
Question 2: In gas chromatography (GC), what is the role of the carrier gas?
- It reacts with the analyte to aid detection
- It serves as the mobile phase to transport analytes through the column (Correct answer)
- It dissolves the stationary phase
- It ionizes the sample for mass spectrometry
Correct answer: It serves as the mobile phase to transport analytes through the column
The carrier gas (e.g., helium or nitrogen) acts as the mobile phase, moving analytes through the GC column.
Question 3: What does the retention time in chromatography indicate?
- The concentration of the analyte
- The time a compound takes to travel from injection to detection (Correct answer)
- The polarity of the mobile phase
- The temperature of the column
Correct answer: The time a compound takes to travel from injection to detection
Retention time is the elapsed time from sample injection to the peak maximum of a compound at the detector.
Question 4: Which type of electrode is used as a reference with a constant, known potential in electroanalytical measurements?
- Working electrode
- Counter electrode
- Standard hydrogen electrode only
- Calomel or Ag/AgCl electrode (Correct answer)
Correct answer: Calomel or Ag/AgCl electrode
The saturated calomel electrode (SCE) and Ag/AgCl electrode are common reference electrodes with stable, reproducible potentials.
Question 5: In Beer-Lambert Law (A = εbc), what does ε represent?
- Path length of the cuvette
- Concentration of the analyte
- Molar absorptivity of the analyte (Correct answer)
- Absorbance reading
Correct answer: Molar absorptivity of the analyte
ε (epsilon) is the molar absorptivity, a substance-specific constant expressing how strongly a compound absorbs light at a given wavelength.
Question 6: What analytical technique measures the mass-to-charge ratio (m/z) of ions to identify compounds?
- Infrared spectroscopy
- Mass spectrometry (Correct answer)
- Nuclear magnetic resonance
- Atomic absorption spectroscopy
Correct answer: Mass spectrometry
Mass spectrometry ionizes compounds and separates them by their mass-to-charge ratio to provide molecular and structural information.
Question 7: Which statistical measure describes the spread of repeated measurements around their mean in analytical chemistry?
- Accuracy
- Bias
- Standard deviation (Correct answer)
- Sensitivity
Correct answer: Standard deviation
Standard deviation quantifies the dispersion of data points around the mean, representing the precision of a measurement set.
Chemistry Test Analytical Chemistry 2
Which technique separates compounds based on their different rates of migration through a stationary phase under a mobile phase?