GACE Chemistry 5 — Questions and Answers
Question 1: Which of the following represents a beta-minus (β⁻) decay reaction?
- A nucleus emits a helium-4 nucleus
- A nucleus emits an electron and an antineutrino (Correct answer)
- A nucleus emits a high-energy photon
- A nucleus captures an orbital electron
Correct answer: A nucleus emits an electron and an antineutrino
Beta-minus decay occurs when a neutron converts to a proton, emitting an electron (beta particle) and an antineutrino.
Question 2: What does a negative ΔG (Gibbs free energy) value indicate about a chemical reaction?
- The reaction is endothermic
- The reaction is nonspontaneous
- The reaction is spontaneous under given conditions (Correct answer)
- The reaction has a high activation energy
Correct answer: The reaction is spontaneous under given conditions
A negative ΔG means the reaction releases free energy and proceeds spontaneously without continuous external energy input.
Question 3: Which separation technique is most appropriate for separating a mixture of compounds based on their differential affinity for a stationary phase versus a mobile phase?
- Distillation
- Filtration
- Chromatography (Correct answer)
- Crystallization
Correct answer: Chromatography
Chromatography separates compounds by exploiting differences in how strongly each component interacts with the stationary phase compared to the mobile phase.
Question 4: Which of the following molecules is nonpolar despite containing polar bonds?
- HCl
- H₂O
- NH₃
- CO₂ (Correct answer)
Correct answer: CO₂
CO₂ has two polar C=O bonds, but they are arranged linearly and their dipoles cancel, making the molecule nonpolar.
Question 5: What is the percent yield if a reaction theoretically produces 50.0 g of product but only 38.5 g is actually collected?
- 56.7%
- 67.5%
- 77.0% (Correct answer)
- 87.5%
Correct answer: 77.0%
Percent yield = (actual yield / theoretical yield) × 100 = (38.5 / 50.0) × 100 = 77.0%.
Question 6: Which of the following functional groups is characteristic of alcohols?
- –COOH
- –CHO
- –OH (Correct answer)
- –NH₂
Correct answer: –OH
Alcohols are defined by the presence of a hydroxyl (–OH) group bonded to a carbon atom.
Question 7: A teacher is designing a lab to demonstrate conservation of mass. Which activity would BEST illustrate this law?
- Dissolving sugar in water and measuring temperature change
- Burning a candle and observing the flame color
- Reacting baking soda and vinegar in a sealed container and comparing mass before and after (Correct answer)
- Mixing food dye in water to study diffusion
Correct answer: Reacting baking soda and vinegar in a sealed container and comparing mass before and after
Using a sealed container ensures no matter escapes, so students can measure that total mass is unchanged before and after the chemical reaction.
GACE Chemistry 5
Which of the following represents a beta-minus (β⁻) decay reaction?