OAT General Chemistry 5 — Questions and Answers
Question 1: Which of the following is the correct electron configuration for Fe²⁺?
- [Ar] 3d⁶ 4s²
- [Ar] 3d⁶ (Correct answer)
- [Ar] 3d⁴ 4s²
- [Ar] 3d⁵ 4s¹
Correct answer: [Ar] 3d⁶
Fe is [Ar]3d⁶4s²; Fe²⁺ loses the two 4s electrons first, giving [Ar]3d⁶.
Question 2: The Nernst equation is used to calculate:
- Activation energy from temperature data
- Cell potential under non-standard conditions (Correct answer)
- Rate constant at equilibrium
- Gibbs free energy at absolute zero
Correct answer: Cell potential under non-standard conditions
The Nernst equation relates cell potential to concentration: E = E° - (RT/nF)ln(Q).
Question 3: Which of the following statements about enthalpy (ΔH) is correct?
- ΔH is always negative for spontaneous reactions
- ΔH of formation for an element in its standard state is zero (Correct answer)
- ΔH depends on the pathway of the reaction
- ΔH is defined only for gas-phase reactions
Correct answer: ΔH of formation for an element in its standard state is zero
By definition, the standard enthalpy of formation for any element in its standard state is zero.
Question 4: In the reaction 2H2O2 → 2H2O + O2, hydrogen peroxide acts as:
- Only an oxidizing agent
- Only a reducing agent
- Both an oxidizing and reducing agent (Correct answer)
- Neither an oxidizing nor reducing agent
Correct answer: Both an oxidizing and reducing agent
H2O2 undergoes disproportionation: one molecule is oxidized (O goes from -1 to 0) and another is reduced (O goes from -1 to -2).
Question 5: Which of the following acids is considered a strong acid?
- Acetic acid (CH3COOH)
- Hydrofluoric acid (HF)
- Nitric acid (HNO3) (Correct answer)
- Phosphoric acid (H3PO4)
Correct answer: Nitric acid (HNO3)
Nitric acid (HNO3) is one of the seven strong acids that dissociate completely in aqueous solution.
Question 6: What is the de Broglie wavelength of a particle?
- Directly proportional to its velocity
- Inversely proportional to its momentum (Correct answer)
- Equal to its kinetic energy divided by Planck's constant
- Independent of the particle's mass
Correct answer: Inversely proportional to its momentum
The de Broglie wavelength λ = h/mv, so wavelength is inversely proportional to momentum (mv).
Question 7: Which of the following compounds exhibits the greatest degree of ionic character?
- HCl
- HI
- NaCl (Correct answer)
- CCl4
Correct answer: NaCl
NaCl has the greatest ionic character because it involves a metal and nonmetal with a large electronegativity difference.
OAT General Chemistry 5
Which of the following is the correct electron configuration for Fe²⁺?