HESI A2 Chemistry Questions

Correct Answer: B

Rationale: The correct answer is B: periods. Periods are the horizontal rows in the periodic table that represent the energy levels of the elements. They indicate the number of electron shells present in an element. Groups (A) are the vertical columns, representing elements with similar chemical properties. Families (C) are also vertical columns that share similar characteristics. Sets (D) is a generic term and not specific to the periodic table structure. Therefore, the correct term for the horizontal rows of the periodic table is periods.

Correct Answer: A

Rationale: The correct answer is A: By lowering the pressure. When pressure is decreased, the boiling point of water also decreases, allowing it to boil at room temperature. Lower pressure reduces the amount of energy needed for water molecules to escape into the gas phase. Increasing pressure (Choice B) raises the boiling point, making it harder to boil at room temperature. Decreasing the volume (Choice C) is not directly related to the boiling point of water. Raising the boiling point (Choice D) would require increasing pressure, contradicting the premise of boiling at room temperature.

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: Neutralization reaction. In this reaction, an acid and a base combine to form water and a salt. This process involves the transfer of protons from the acid to the base, resulting in the formation of water and a salt. Neutralization reactions are characterized by the formation of a neutral product (water) from the acidic and basic reactants. Option B: Decomposition reaction involves a compound breaking down into simpler substances. Option C: Combustion reaction involves a substance reacting with oxygen to produce heat and light. Option D: Redox reaction involves the transfer of electrons between reactants. These options do not accurately describe the reaction between an acid and a base to form water and salt.

Correct Answer: A

Rationale: The correct answer is A: Freezing point depression. Colligative properties depend on the number of solute particles in a solution, not the nature of the solute. Freezing point depression occurs because the presence of solute particles disrupts the formation of orderly ice crystals, lowering the freezing point of the solution. Viscosity and surface tension are not colligative properties as they are not solely dependent on the number of solute particles. Boiling point elevation is a colligative property, but the question specifically asks for a property related to freezing, making it incorrect in this context.