OAT General Chemistry Principles 5 — Questions and Answers
Question 1: Which of the following best describes the relationship between Kp and Kc for a gas-phase reaction?
- Kp = Kc always
- Kp = Kc(RT)^Δn (Correct answer)
- Kp = Kc/RT
- Kp = Kc + Δn
Correct answer: Kp = Kc(RT)^Δn
The relationship is Kp = Kc(RT)^Δn, where Δn is the change in moles of gas (products minus reactants).
Question 2: What type of radioactive decay results in an increase in atomic number by 1?
- Alpha decay
- Beta-minus decay (Correct answer)
- Gamma decay
- Positron emission
Correct answer: Beta-minus decay
In beta-minus decay, a neutron is converted to a proton, emitting an electron, which increases the atomic number by 1.
Question 3: A 1 L solution contains 0.5 mol of HF (Ka = 7.2 × 10⁻⁴). Compared to 0.5 M HCl, the HF solution has:
- A higher pH (Correct answer)
- A lower pH
- The same pH
- A pH of exactly 7
Correct answer: A higher pH
HF is a weak acid that only partially dissociates, producing fewer H⁺ ions than strong acid HCl at the same concentration, resulting in a higher pH.
Question 4: Which of the following has the greatest electronegativity?
- Na
- Cl
- F (Correct answer)
- O
Correct answer: F
Fluorine has the highest electronegativity (3.98 on the Pauling scale) of all elements.
Question 5: The standard electrode potential (E°) of a cell reaction is +1.10 V. This reaction is:
- Non-spontaneous, ΔG° > 0
- Spontaneous, ΔG° < 0 (Correct answer)
- At equilibrium, ΔG° = 0
- Spontaneous only at high temperature
Correct answer: Spontaneous, ΔG° < 0
A positive E°cell corresponds to a negative ΔG° (ΔG° = −nFE°), indicating a spontaneous reaction under standard conditions.
Question 6: Which law states that at constant temperature, the volume of a gas is inversely proportional to its pressure?
- Charles's Law
- Avogadro's Law
- Boyle's Law (Correct answer)
- Gay-Lussac's Law
Correct answer: Boyle's Law
Boyle's Law states that P₁V₁ = P₂V₂ at constant temperature, showing an inverse pressure-volume relationship.
Question 7: Which of the following is a colligative property?
- Color of the solution
- Viscosity
- Osmotic pressure (Correct answer)
- Reactivity with acids
Correct answer: Osmotic pressure
Osmotic pressure is a colligative property because it depends only on the number of solute particles, not their identity.
OAT General Chemistry Principles 5
Which of the following best describes the relationship between Kp and Kc for a gas-phase reaction?