HESI A2 Chemistry Questions

Correct Answer: B

Rationale: The correct answer is B: Condensation. Condensation is the process in which a gas turns into a liquid by losing heat energy. During condensation, gas molecules slow down and come closer together, forming liquid droplets. Sublimation (A) is the process of a solid turning directly into a gas without passing through the liquid phase. Evaporation (C) is the process of a liquid turning into a gas. Deposition (D) is the process in which a gas transforms directly into a solid without becoming a liquid first.

Correct Answer: B

Rationale: The correct answer is B: Group 1 contains the alkali metals. Alkali metals are found in Group 1 because they have a single valence electron, making them highly reactive. They exhibit similar properties due to the presence of this single electron. Group 7 contains the halogens and is known for its high reactivity. Group 2 contains the alkaline earth metals, which have two valence electrons. Group 3 contains the transition metals, which have varying numbers of valence electrons and are less reactive compared to alkali metals. Thus, Group 1 is the only group that fits the characteristics of alkali metals.

Correct Answer: A

Rationale: The correct answer is A: boron. Diatomic molecules consist of two atoms of the same element bonded together. Boron exists as a monatomic element, meaning it exists as single atoms. Fluorine, oxygen, and nitrogen exist naturally as diatomic molecules (F2, O2, N2) due to their stability when bonded together. Boron does not form diatomic molecules because it is less stable in that form.

Correct Answer: A

Rationale: The correct answer is A: mass spectrometer. A mass spectrometer separates gaseous ions based on their mass-to-charge ratio by ionizing the sample, accelerating the ions, and then analyzing their deflection in a magnetic field. This process allows for the determination of the molecular weight of compounds. B: Interferometer measures interference patterns, not mass-to-charge ratios. C: Magnetometer measures magnetic fields, not ion mass-to-charge ratios. D: Capacitance meter measures capacitance, not mass-to-charge ratios.

Correct Answer: B

Rationale: The correct answer is B: Production of gas. In a chemical change, new substances are formed with different properties. The production of gas is a sign of a chemical reaction due to the formation of new molecules. Choices A, C, and D are physical changes, not chemical changes. A change in shape (A) is a physical change as it does not alter the chemical composition. Melting (C) and freezing (D) are also physical changes, involving the state of matter without changing the chemical composition.