OAT General Chemistry 2 — Questions and Answers
Question 1: Which quantum number describes 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 is BEST described as one that:
- Resists changes in temperature
- Maintains constant ionic strength
- Resists changes in pH upon addition of small amounts of acid or base (Correct answer)
- Prevents precipitation of salts
Correct answer: Resists changes in pH upon addition of small amounts of acid or base
A buffer resists pH changes by containing a weak acid and its conjugate base (or weak base and conjugate acid).
Question 3: What is the oxidation state of sulfur in H2SO4?
- +4
- +6 (Correct answer)
- +2
- -2
Correct answer: +6
In H2SO4, hydrogen is +1 and oxygen is -2, so sulfur must be +6 to balance the neutral molecule.
Question 4: According to VSEPR theory, what is the molecular geometry of SF4?
- Tetrahedral
- See-saw (Correct answer)
- Square planar
- Trigonal pyramidal
Correct answer: See-saw
SF4 has 4 bonding pairs and 1 lone pair on sulfur, giving it a see-saw (seesaw) geometry.
Question 5: Which of the following has the highest boiling point?
- CH4
- NH3 (Correct answer)
- PH3
- SiH4
Correct answer: NH3
NH3 has the highest boiling point due to strong intermolecular hydrogen bonding.
Question 6: For a reaction with ΔG = 0, which statement is TRUE?
- The reaction is non-spontaneous
- The system is at equilibrium (Correct answer)
- No products have formed
- The enthalpy equals zero
Correct answer: The system is at equilibrium
ΔG = 0 indicates the system is at equilibrium, where forward and reverse reaction rates are equal.
Question 7: Which type of radioactive decay increases the atomic number by 1?
- Alpha decay
- Beta-minus decay (Correct answer)
- Gamma decay
- Positron emission
Correct answer: Beta-minus decay
Beta-minus decay converts a neutron to a proton and emits an electron, increasing atomic number by 1.
OAT General Chemistry 2
Which quantum number describes the shape of an atomic orbital?