Answer: A. Primary, secondary, and tertiary carbon atoms in a molecule

Explanation: DEPT (Distortionless Enhancement by Polarization Transfer) experiments in NMR help differentiate between primary, secondary, and tertiary carbons by showing distinct signal patterns based on the number of attached protons.

Answer: C. AFM

Explanation: Atomic Force Microscopy (AFM) can be used to study the surface contours of proteins at the nanoscale. It provides high-resolution topographical data without requiring extensive sample preparation.

Answer: C. 2-Pentanol

Explanation: 2-Pentanol does not show a positive iodoform test because it lacks the methyl ketone group or an equivalent structure necessary for the reaction, unlike 2-butanone and acetaldehyde.

Answer: A. -OH alcohol

Explanation: A strong absorption near 3400 cm⁻¹ in an IR spectrum typically indicates the presence of an O–H group, such as in alcohols. This signal results from the stretching vibration of hydroxyl groups.

Answer: B. Uric acid

Explanation: The murexide test is a qualitative test used for the detection of uric acid. When uric acid reacts with nitric acid and is subsequently heated, a murexide (purple) color develops, confirming its presence.

Answer: A. Cyanide ion by titration with silver nitrate

Explanation: The Volhard method is an analytical titration technique used for the estimation of cyanide ions. It involves titrating with silver nitrate after precipitating the cyanide, making it an important method in analytical chemistry.

Answer: D. Tannins

Explanation: The matchstick test is a qualitative assay used to detect the presence of tannins in a sample. Tannins react with specific reagents to produce a color change, confirming their presence in plant extracts.

Answer: C. Limulus Amoebocyte Lysate

Explanation: LAL stands for Limulus Amoebocyte Lysate, a reagent derived from horseshoe crab blood that is used for detecting bacterial endotoxins in pharmaceuticals and medical devices.

Answer: C. ESR

Explanation: DPPH (2,2-diphenyl-1-picrylhydrazyl) is commonly used as an internal standard in Electron Spin Resonance (ESR) spectroscopy to measure free radicals and antioxidant activity in a sample.

Answer: D. 240 nm

Explanation: Chloroform has a UV cut off of approximately 240 nm, meaning it does not absorb light significantly below this wavelength. This property is important when selecting solvents for UV spectroscopy.

Answer: B. Kjeldahl

Explanation: The Kjeldahl method is a widely used chemical method for determining the nitrogen content in substances. This method is critical in evaluating protein content and other nitrogen-containing compounds in various samples.

Answer: B. Aldose and ketose sugars

Explanation: Seliwanoff's test differentiates aldose sugars from ketose sugars based on their reaction rate with resorcinol under acidic conditions, with ketoses reacting faster to produce a characteristic color.

Answer: C. 2,2-Dimethylpropane

Explanation: A compound that gives one proton signal in ¹H NMR and two signals in ¹³C NMR is highly symmetric. 2,2-Dimethylpropane (neopentane) fits this description, showing a single environment for protons and two distinct carbon environments.

Answer: C. Bond dipole during vibration

Explanation: For a bond to absorb infrared radiation, there must be a change in the dipole moment during vibration. This change in bond dipole is critical for the IR activity of a molecular vibration.

Answer: C. Rault's law

Explanation: Azeotropes occur when a mixture shows a significant deviation from Raoult’s law. This deviation leads to a constant boiling mixture where the composition of the vapor is the same as that of the liquid.

Answer: D. Methylene blue

Explanation: Methylene blue is commonly used as an indicator in redox titrations. It changes color when reduced, providing a visual signal that helps determine the endpoint of the titration.

Answer: C. 1600-1500 and 1400-1300

Explanation: The nitro group (NO₂) in nitroalkanes shows characteristic stretching vibrations in the ranges 1600–1500 cm⁻¹ and 1400–1300 cm⁻¹, which are used to identify nitro compounds by IR spectroscopy.

Answer: A. NF₃

Explanation: NF₃ has a non-zero dipole moment due to the asymmetrical distribution of electronegativity among its atoms. In contrast, molecules like CCl₄ and CO₂ are symmetrical and have zero dipole moments.

Answer: A. 3σ/S

Explanation: The detection limit in analytical chemistry is calculated using the formula 3σ/S, where σ is the standard deviation of the blank and S is the slope of the calibration curve. This value indicates the lowest concentration that can be reliably detected.

Answer: D. -CN

Explanation: Among the options given, the -CN group is highly electron-withdrawing and deactivating; however, based on the provided answer, -CN is considered most activating in this context, which might reflect the verbatim answer from the exam despite conventional expectations.