MCAT Chemistry 2

Question 1

Which of the following best describes a buffer solution?

Accepted Answer

A solution that resists changes in pH when small amounts of acid or base are added

Answer

A buffer resists pH changes because it contains a weak acid and its conjugate base (or weak base and conjugate acid) that can absorb added H⁺ or OH⁻.

Question 2

What is the hybridization of the carbon atom in CO₂?

Accepted Answer

sp

Answer

Carbon in CO₂ forms two double bonds with oxygen, requiring two sp hybrid orbitals and two unhybridized p orbitals for the π bonds.

Question 3

Which quantum number describes the shape of an orbital?

Accepted Answer

Angular momentum quantum number (l)

Answer

The angular momentum quantum number (l) determines the shape of the orbital: l=0 is s (spherical), l=1 is p (dumbbell), l=2 is d.

Question 4

A reaction has ΔG° = +20 kJ/mol at 298 K. Which statement is correct?

Accepted Answer

The equilibrium constant K < 1

Answer

A positive ΔG° means the reaction is non-spontaneous under standard conditions, and since ΔG° = -RT ln K, a positive ΔG° requires K < 1.

Question 5

In an SN2 reaction, the rate depends on which of the following?

Accepted Answer

Both the concentration of the substrate and nucleophile

Answer

SN2 is a bimolecular reaction with a concerted mechanism where the nucleophile attacks as the leaving group departs, so rate = k[substrate][nucleophile].

MCAT - Medical College Admission Test Practice Test

MCAT - Medical College Admission Test Practice Test

MCAT Chemistry 2