MChem Master of Chemistry Computational Chemistry 3

Question 1

In QSAR (Quantitative Structure-Activity Relationship) modeling, what are molecular descriptors?

Accepted Answer

Numerical representations of molecular features used to predict properties

Answer

Molecular descriptors are calculated numerical features (e.g., logP, topological indices) that correlate molecular structure with biological or chemical activity.

Question 2

What is the 'zero-point energy' (ZPE) correction important for in computational thermochemistry?

Accepted Answer

It corrects for the residual vibrational energy at 0 K

Answer

ZPE arises from quantum mechanical vibrational motion that persists even at absolute zero and must be included for accurate thermochemical predictions.

Question 3

In free energy perturbation (FEP) calculations, what is being computed?

Accepted Answer

The free energy difference between two states via alchemical transformations

Answer

FEP computes free energy differences by gradually transforming one molecular state into another through unphysical (alchemical) intermediate states.

Question 4

Which property does a Mulliken population analysis calculate?

Accepted Answer

Partial atomic charges from the electron density

Answer

Mulliken population analysis partitions the electron density among atoms to assign partial charges, though it is basis-set dependent.

Question 5

What does the acronym CCSD(T) stand for, and why is it considered the 'gold standard' in quantum chemistry?

Accepted Answer

Coupled Cluster Singles Doubles and perturbative Triples — high accuracy near the full CI limit

Answer

CCSD(T) includes singles, doubles, and perturbative triple excitations, providing near-exact accuracy for energetics of molecules near their equilibrium geometry.

MChem Master of Chemistry Practice Test

MChem Master of Chemistry Practice Test

MChem Master of Chemistry Computational Chemistry 3