OAT General Chemistry Principles 2 — Questions and Answers
Question 1: Which quantum number determines the shape of an atomic orbital?
- Principal quantum number (n)
- Angular momentum quantum number (l) (Correct answer)
- Magnetic quantum number (ml)
- Spin quantum number (ms)
Correct answer: Angular momentum quantum number (l)
The angular momentum quantum number (l) determines the shape of the orbital (s, p, d, f).
Question 2: A buffer solution resists pH change best when the pH equals the:
- Kb of the conjugate base
- pKa of the weak acid (Correct answer)
- pKw minus the pKb
- Concentration of the salt
Correct answer: pKa of the weak acid
A buffer is most effective when pH = pKa, where the concentrations of weak acid and conjugate base are equal (Henderson-Hasselbalch equation).
Question 3: What is the hybridization of the central carbon in CO2?
- sp3
- sp2
- sp (Correct answer)
- sp3d
Correct answer: sp
Carbon in CO2 forms two double bonds with no lone pairs, resulting in sp hybridization and linear geometry.
Question 4: During a reaction, ΔG = 0. This indicates the reaction is:
- Spontaneous in both directions
- At equilibrium (Correct answer)
- Non-spontaneous
- Exothermic
Correct answer: At equilibrium
When ΔG = 0, the system is at chemical equilibrium and the forward and reverse rates are equal.
Question 5: Which of the following exhibits the highest boiling point due to intermolecular forces?
- CH4
- NH3 (Correct answer)
- PH3
- SiH4
Correct answer: NH3
NH3 has the highest boiling point because it can form hydrogen bonds, which are stronger than the London dispersion forces present in the others.
Question 6: In a galvanic cell, oxidation occurs at the:
- Cathode
- Salt bridge
- Anode (Correct answer)
- External circuit
Correct answer: Anode
Oxidation (loss of electrons) always occurs at the anode of an electrochemical cell.
Question 7: The rate law for a reaction is rate = k[A]²[B]. If [A] is doubled while [B] is held constant, the rate will:
- Double
- Triple
- Quadruple (Correct answer)
- Increase eightfold
Correct answer: Quadruple
Because the reaction is second order in A, doubling [A] increases the rate by a factor of 2² = 4.
OAT General Chemistry Principles 2
Which quantum number determines the shape of an atomic orbital?