QC II LAB - Modules 7 & 8 (T or F Practice)

True

The pKa of a drug is a critical parameter because it influences pH-dependent solubility, bioavailability, and gastrointestinal absorption.

True

According to the Henderson-Hasselbalch equation, when the pH of a solution is equal to the pKa of the acid, the concentration of the ionized form is equal to the concentration of the unionized form.

False; there’s potentiometry, spectrofluorometry, and HP

UV spectrometry is the only method available for determining the pKa of a pharmaceutical substance.

False; longer wavelength and known as “red shift”

A bathochromic shift refers to a shift in the absorption maximum to a shorter wavelength, also known as a "blue shift."

True

Beer-Lambert's Law may not be applicable in cases of high concentration or when the solute undergoes association or dissociation.

True

In order for a molecule to absorb IR radiation, it must undergo a net change in its dipole moment as a consequence of its vibrational motion.

False; they are bending modes

"Scissoring" and "rocking" are types of stretching vibrational modes in IR absorption.

True

The "Fingerprint region" of an IR spectrum (below 1500 cm-1) is unique for every molecule and can be used for absolute identification.

False ; broad and strong

The O-H absorption band in alcohols is typically characterized as narrow and weak.

True

Primary amides and primary amines are characterized by a doublet peak in the N-H stretching region (3500--3100 cm-1).

True

The carbonyl group (C=O) stretch typically appears in Zone 4, between 1950 cm-1 and 1650 cm-1.

False; only 1%

In the preparation of KBr disks for solid samples, the sample usually makes up about 50% of the total weight of the mixture.

True

The "isobestic point" is the specific wavelength where two or more chemical species have the exact same absorbance.

True

An increase in temperature usually results in a decrease in the viscosity of a solution, which can influence its absorbance.

False; it’s for the unionized form

In the UV spectrometric determination of pKa, AHA represents the absorbance of the fully ionized form of the molecule.

True

High electrolyte concentrations in a solution are a known variable that can influence absorbance readings.

True

A "Hyperchromic shift" refers to an increase in the intensity of the absorption (higher absorbance).

True

The Double-Bond Equivalent (DBE) formula is used to calculate the number of rings and double bonds based on the empirical formula.

True

According to the IR functional group zones, triple bonds (alkynes and nitriles) are typically found in Zone 3 (2300--2100 cm-1).

True

Benzoic acid shows a broader O-H stretch compared to alcohols due to strong hydrogen bonding.

True

Esters, such as methyl benzoate, do not show an O-H stretching band in the IR spectrum.

False; it’s a detector

In an IR spectrometer, the thermocouple acts as the source of infrared radiation.

True

The term "neat" in sample preparation refers to analyzing a liquid in its pure form without a solvent.

False; because it is replaced by a metal ion

Carboxylic acid salts (like sodium benzoate) will typically show the same broad O-H stretch as their corresponding carboxylic acids.