Answer: D. FID

Explanation: Flame Ionization Detectors (FID) are commonly used in gas chromatography for detecting organic compounds because they provide a wide linear range and high sensitivity for carbon-containing species.

Answer: C. 1-butyne

Explanation: 1-butyne exhibits a sharp IR absorption band around 3300 cm⁻¹ due to the ≡C–H stretch. This feature is distinct from the vibrations seen in dienes or internal alkynes.

Answer: A. Potassium sodium tartrate

Explanation: Rochelle salt is the common name for potassium sodium tartrate, a double salt used in various industrial processes including as a component in dyeing and as a complexing agent.

Answer: C. Sodium tartrate dihydrate

Explanation: Karl Fischer titration, used for water determination, is standardized with sodium tartrate dihydrate. This standardization ensures accurate measurement of water content in various substances.

Answer: B. Two signals, each as singlet

Explanation: The NMR spectrum of diethyl ether typically shows two singlets corresponding to the two different proton environments. The molecule’s symmetry causes the two sets of protons to appear as distinct, non-coupled signals.

Answer: D. Fermi resonance

Explanation: Weak bands observed at 2750 and 2850 cm⁻¹ in aldehydes are attributed to Fermi resonance, which occurs when overtone or combination bands interact with fundamental vibrations, resulting in shifts in absorption intensity.

Answer: D. Either a or c could be correct

Explanation: Tetrahydrofuran exhibits symmetry leading to two distinct proton environments. Depending on subtle conformational differences, the signals may appear as either a doublet and a triplet or vice versa, making both patterns acceptable.

Answer: D. HPLC

Explanation: High Performance Liquid Chromatography (HPLC) is widely used for impurity profiling in drug substances due to its high sensitivity, precision, and ability to separate complex mixtures for quantification.

Answer: D. Free radical formation

Explanation: APS is used in SDS-PAGE to generate free radicals that initiate the polymerization of acrylamide, forming the polyacrylamide gel matrix essential for protein separation.

Answer: C. 91

Explanation: In the mass spectrum of benzyl alcohol, the base peak is typically observed at m/z 91, corresponding to the tropylium ion, which is a stable fragment formed during the ionization process.

Answer: D. High, Large, Short

Explanation: High-energy electromagnetic radiation is characterized by high frequencies, large wavenumbers, and short wavelengths. This combination is found in the ultraviolet and X-ray regions of the spectrum.

Answer: D. Largest intensity of overtone

Explanation: The Franck-Condon Principle explains the intensity distribution in vibrational transitions. It can account for the unexpectedly high intensity of overtone bands under certain conditions due to favorable overlap of vibrational wave functions.

Answer: A. 58000

Explanation: A 0.1 M NaCl solution corresponds to approximately 58000 ppm. This conversion from molarity to parts per million is based on the molar mass and density of the solution, making it a useful calculation in analytical chemistry.

Answer: B. Helium

Explanation: Helium is commonly used in pycnometry because of its low density and inert nature. It easily penetrates small spaces, allowing for accurate measurement of the true density of a sample.

Answer: D. Bulk density

Explanation: Bulk density is a derived property that depends on the packing and arrangement of particles in a substance. It is not an intrinsic property like pKa, but it is critical in formulation and processing.

Answer: D. HPLC

Explanation: HPLC is not used for moisture determination. Moisture content is typically measured by techniques such as Karl Fischer titration (KF titration), Thermogravimetric Analysis (TGA), or specialized IR balances.

Answer: B. Colligative

Explanation: Colligative properties depend on the number of solute particles in a solution rather than their chemical nature. These properties include boiling point elevation, freezing point depression, and osmotic pressure.

Answer: A. Benzene and Toluene

Explanation: Benzene and toluene form an ideal solution because their molecular interactions are similar, resulting in linear concentration-dependent properties that obey Raoult's law.

Answer: B. Triplet to singlet transition

Explanation: Phosphorescence arises from the transition of an excited species from a triplet state to a singlet ground state. This process is spin-forbidden, resulting in longer emission lifetimes compared to fluorescence.

Answer: B. √2

Explanation: In certain screening processes, the ratio of the actual mesh dimension of a Taylor series to that of the next smaller screen is √2. This mathematical relationship is applied in particle size analysis and filtration studies.