MCAT Chemistry 5

Question 1

Which of the following describes the relationship between vapor pressure and temperature?

Accepted Answer

Vapor pressure increases as temperature increases

Answer

As temperature increases, more molecules have sufficient kinetic energy to escape the liquid phase, increasing vapor pressure according to the Clausius-Clapeyron equation.

Question 2

In a mass spectrometer, the molecular ion peak (M⁺) represents:

Accepted Answer

The molecule after losing one electron, giving its molecular weight

Answer

The molecular ion peak (M⁺) appears when the molecule loses one electron without fragmenting, giving a peak at the molecular weight of the compound.

Question 3

Which of the following correctly describes Hess's Law?

Accepted Answer

The total enthalpy change for a reaction equals the sum of enthalpy changes for individual steps

Answer

Hess's Law states that since enthalpy is a state function, the total ΔH for a reaction is the sum of ΔH values for each step, regardless of the path taken.

Question 4

Which of the following best describes a sigma (σ) bond?

Accepted Answer

A bond formed by the head-on overlap of orbitals along the internuclear axis

Answer

A sigma bond forms from head-on (end-to-end) overlap of orbitals along the internuclear axis and allows free rotation; all single bonds are sigma bonds.

Question 5

What is the effect of a catalyst on an equilibrium reaction?

Accepted Answer

It lowers the activation energy of both forward and reverse reactions equally

Answer

A catalyst lowers activation energy for both the forward and reverse reactions equally, increasing the rate at which equilibrium is reached but not changing the equilibrium position or K.

MCAT - Medical College Admission Test Practice Test

MCAT - Medical College Admission Test Practice Test

MCAT Chemistry 5