MS MS in Chemistry 2

Question 1

In gas chromatography (GC), the stationary phase separates compounds primarily based on:

Accepted Answer

Polarity and volatility interactions with the column

Answer

Molecular weight

Answer

Ionic charge

Answer

Refractive index

Question 2

The Henderson-Hasselbalch equation, pH = pKa + log([A−]/[HA]), is most useful for:

Accepted Answer

Calculating buffer pH when the ratio of conjugate base to weak acid is known

Answer

Strong acid titrations near the equivalence point

Answer

Predicting solubility of sparingly soluble salts

Answer

Determining electrode potentials in electrochemical cells

Question 3

Which electrochemical technique measures the current as a function of applied potential while analyte concentration is varied to generate calibration data?

Accepted Answer

Voltammetry

Answer

Potentiometry

Answer

Coulometry

Answer

Conductimetry

Question 4

In HPLC with a reverse-phase column, which solvent system would elute a polar compound first?

Accepted Answer

90% water / 10% acetonitrile

Answer

100% acetonitrile

Answer

50% water / 50% methanol

Answer

100% methanol

Question 5

Beer-Lambert Law (A = εbc) relates absorbance to concentration. If you double the path length (b) while halving the concentration (c), absorbance will:

Accepted Answer

Remain the same

Answer

Double

Answer

Halve

Answer

Quadruple

Question 6

In inductively coupled plasma–mass spectrometry (ICP-MS), the plasma temperature (~6,000–10,000 K) primarily serves to:

Accepted Answer

Ionize analyte atoms for mass analysis

Answer

Separate isotopes based on charge

Answer

Vaporize the solvent only

Answer

Reduce polyatomic interferences

Question 7

Which statistical parameter describes the precision of an analytical method by expressing the standard deviation as a percentage of the mean?

Accepted Answer

Coefficient of variation (CV%)

Answer

Limit of detection (LOD)

Answer

Bias

Answer

Recovery percentage