MCAT Chemistry 4

Question 1

Which of the following describes Le Chatelier's principle?

Accepted Answer

A system at equilibrium will shift to counteract any imposed change in conditions

Answer

Le Chatelier's principle states that a system in equilibrium will respond to stress (changes in concentration, pressure, or temperature) by shifting to partially counteract the disturbance.

Question 2

In organic chemistry, which functional group is present in amines?

Accepted Answer

–NH₂ (amino)

Answer

Amines contain a nitrogen atom bonded to hydrogen and/or carbon atoms; primary amines have the –NH₂ functional group.

Question 3

Which of the following best describes what happens during saponification?

Accepted Answer

An ester reacts with a strong base to form a carboxylate salt and an alcohol

Answer

Saponification is the base-catalyzed hydrolysis of an ester, producing a carboxylate salt and alcohol; it is the chemical basis of soap-making from triglycerides.

Question 4

Which of the following molecules is most likely to exhibit resonance?

Accepted Answer

C₆H₆ (benzene)

Answer

Benzene exhibits resonance because its delocalized π electrons can be represented by multiple equivalent Lewis structures with alternating single and double bonds.

Question 5

A solution contains 0.1 mol/L of a weak acid with Ka = 1×10⁻⁵. What is the approximate pH?

Accepted Answer

3.0

Answer

For a weak acid, [H⁺] ≈ √(Ka × C) = √(1×10⁻⁵ × 0.1) = √(1×10⁻⁶) = 1×10⁻³, so pH = 3.

MCAT - Medical College Admission Test Practice Test

MCAT - Medical College Admission Test Practice Test

MCAT Chemistry 4