Answer: B. Voltage

Explanation: In amperometric titrations, the potential difference (voltage) is kept constant while the current is measured, providing quantitative information about the analyte.

Answer: B. Organic stationary phase

Explanation: Reverse phase chromatography features a nonpolar (organic) stationary phase and a polar mobile phase, allowing separation based on hydrophobic interactions.

Answer: A. Sucrose

Explanation: Sucrose is a non-reducing sugar because its anomeric carbons are involved in the glycosidic bond, preventing it from acting as a reducing agent.

Answer: C. Gel permeation

Explanation: Gel permeation chromatography separates molecules based solely on their size and shape, without chemical interactions.

Answer: D. Microwave

Explanation: Electron spin resonance (ESR) spectroscopy typically uses microwave radiation to excite unpaired electrons in a magnetic field.

Answer: B. 2

Explanation: Due to the high symmetry of 1,4-dibromobenzene, there are only two unique carbon environments, so only two signals appear in its ¹³C NMR spectrum.

Answer: A. I-P, II-Q, III-R

Explanation: The calibration of UV instruments uses standard solutions: K₂Cr₂O₇ in H₂SO₄ for absorbance control, 1.2% KCl for stray light, and a toluene solution for resolution power.

Answer: B. 354

Explanation: 254

Answer: C. CNMR

Explanation: In carbon-13 NMR spectroscopy, valleys (or signal intensities) can provide useful information about the chemical environment of carbons, although peaks are the primary focus.

Answer: D. -196°C

Explanation: Liquid nitrogen has a boiling point of approximately -196°C, making it extremely cold and useful for cryogenic applications.

Answer: D. Geiger-Muller counter

Explanation: A Geiger-Muller counter is a standard instrument for detecting and measuring ionizing radiation, making it ideal for radioactivity measurements.

Answer: B. UPLC

Explanation: Ultra Performance Liquid Chromatography (UPLC) utilizes higher pressures (up to 20,000 psi) than traditional HPLC, allowing for faster and more efficient separations.

Answer: C. 6.7

Explanation: 99% ionization requires pH ≈ pKa + 2 ≈ 4.7, not 6.7.

Answer: C. Transmittance versus wavenumber

Explanation: IR spectra are typically plotted as transmittance versus wavenumber, allowing for identification of functional groups based on characteristic absorption bands.

Answer: B. OH of silica

Explanation: End capping blocks residual free hydroxyl groups (OH) on silica particles, thereby reducing tailing and improving peak shape in reverse phase chromatography.

Answer: A. Photons emitted while excited electrons drop down

Explanation: Luminescence occurs when excited electrons return to lower energy levels and emit photons, producing visible light.

Answer: C. Cyanide

Explanation: Cyanide compounds are notorious for their bitter almond odor and high toxicity, interfering with cellular respiration by inhibiting cytochrome c oxidase.

Answer: C. Pyridine

Explanation: Pyridine generally does not fluoresce due to its electronic structure, while quinoline, isoquinoline, and indole are fluorescent under UV light.

Answer: B. (mol L⁻¹)ⁿ⁻¹ sec⁻¹

Explanation: For an nth order reaction, the rate constant has units of (mol L⁻¹)^(1–n) sec⁻¹; for a second order reaction, this becomes (mol L⁻¹)⁻¹ sec⁻¹.

Answer: A. Bathochromic

Explanation: Alkyl substitution on a chromophore often leads to a bathochromic (red) shift in the UV absorption spectrum due to stabilization of the excited state.