Answer: C. Diffraction grating

Explanation: The diffraction grating in a monochromator is the dispersing element that separates light into its component wavelengths.

Answer: C. Cathode

Explanation: In an electrochemical cell, reduction occurs at the cathode where electrons are gained by the chemical species.

Answer: A. (CH₃CH₂CH₂)₂N

Explanation: Tertiary amines such as (CH₃CH₂CH₂)₂N lack N–H bonds and therefore do not show the broad N–H absorption near 3300 cm⁻¹ unlike the other compounds.

Answer: B. Vibrational

Explanation: Raman spectroscopy is a vibrational spectroscopic technique that measures the inelastic scattering of light. It provides information about molecular vibrations and chemical structure.

Answer: B. INN

Explanation: The International Nonproprietary Name (INN) system is globally recognized for identifying pharmaceutical substances by a unique generic name, ensuring consistency across different markets.

Answer: B. Zeolites

Explanation: Zeolites are crystalline microporous aluminosilicates with a well-defined pore structure. They are widely used as catalysts and adsorbents due to their unique ion-exchange properties.

Answer: A. Above 7

Explanation: Sodium acetate is the salt of a weak acid (acetic acid) and a strong base. Its aqueous solution is basic, so the pH of a 0.1 M solution will be above 7.

Answer: A. Tollens reagent

Explanation: The Tollens test is used to identify aldehydes by forming a silver mirror; ketones do not react. This test distinguishes aldehydes from ketones based on their reducing properties.

Answer: D. Gas Liquid Chromatography

Explanation: After silylation, sucrose becomes volatile and can be separated by gas–liquid chromatography. This derivatization technique is commonly used to analyze sugars in complex mixtures.

Answer: A. The A term

Explanation: In gas chromatography using an open tubular column, the A term (related to eddy diffusion) is negligible because the stationary phase is a thin film, minimizing multiple flow paths.

Answer: B. CH₃ CH₂CH₂CH₂+

Explanation: A fragment ion at m/z 57 typically corresponds to the butyl cation (CH₃CH₂CH₂CH₂+), a common and stable fragment observed in mass spectra of aliphatic compounds.

Answer: A. Conjugated polyenes

Explanation: K-band absorption in the K-region is typically attributed to π → π* transitions in conjugated polyenes, where extended conjugation lowers the energy gap between molecular orbitals.

Answer: D. Decomposition caused by temperature

Explanation: Accelerated stability studies use increased temperatures to predict long-term stability. This approach is based on the Arrhenius equation, which relates reaction rate to temperature.

Answer: D. Ammonia test

Explanation: Aldehydes are typically identified by Brady's, Benedict, and Fehling tests. The ammonia test is not used for aldehyde detection and thus is the correct answer.

Answer: A. Entropy

Explanation: Colligative properties depend on the number of solute particles in solution and are driven by entropy changes. The increase in disorder caused by the dissolved particles lowers the freezing point.

Answer: C. Weak solute-solvent interactions

Explanation: Positive deviations from Raoult’s Law occur when solute-solvent interactions are weak compared to solute-solute and solvent-solvent interactions, leading to higher vapor pressures than predicted.

Answer: C. Rotational

Explanation: Rotational energy changes are typically much smaller than vibrational or electronic transitions. In some cases, the change in rotational quantum number may be too small to be observed in standard spectroscopic techniques.

Answer: C. phenol red

Explanation: Phenol red, with a pKin of 7.9, is most appropriate since its color change occurs at a pH well above the pKa of lactic acid, ensuring a clear endpoint in titration with a strong base.

Answer: C. has lost one electron

Explanation: The molecular ion is formed by the loss of one electron from the parent molecule, resulting in a radical cation. It is a key peak in mass spectrometry that represents the intact molecule.

Answer: C. Accuracy

Explanation: Accuracy refers to how close a measured value is to the true value. It is a measure of systematic error, distinct from precision, which is the reproducibility of measurements.