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: It releases heat. In an exothermic reaction, energy is released in the form of heat to the surroundings. This results in a temperature increase in the surrounding environment. The other choices are incorrect because: A: It absorbs heat - This is a characteristic of an endothermic reaction, where heat is absorbed from the surroundings. C: It remains neutral - This does not describe the nature of an exothermic reaction, which involves the release of heat. D: It requires energy input - This is more in line with an endothermic reaction, where energy input is needed to drive the reaction.

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: Solid. In solids, particles are tightly packed in a fixed position due to strong intermolecular forces holding them in place. This results in a definite shape and volume. In liquids (choice A), particles are close together but not in fixed positions, allowing them to flow and take the shape of their container. In gases (choice C), particles are far apart and move freely, leading to indefinite shape and volume. In plasma (choice D), particles are highly energized, ionized, and not bound together, making them not tightly packed or in fixed positions.

Correct Answer: A

Rationale: The correct answer is A: A reaction that absorbs heat. Endothermic reactions absorb heat from their surroundings, causing a decrease in temperature. This is due to the breaking of chemical bonds which requires energy input. Choice B is incorrect as exothermic reactions release heat. Choice C is incorrect as all reactions involve heat to some extent. Choice D is incorrect as endothermic reactions result in a decrease in temperature due to heat absorption.