HESI A2 Chemistry Questions

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.

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.

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: D

Rationale: The correct answer is D: Glucose. Glucose is a product of photosynthesis, as plants use sunlight, water, and carbon dioxide to produce glucose (sugar) and oxygen. Glucose is a type of carbohydrate that serves as a primary source of energy for plants and other organisms. Carbon dioxide (A) is one of the reactants needed for photosynthesis, not a product. Oxygen (B) is released as a byproduct of photosynthesis, not a product. Water (C) is also a reactant in photosynthesis, not a product. Therefore, the correct answer is D because glucose is the main product of photosynthesis.

Correct Answer: C

Rationale: The correct answer is C: Argon. Noble gases are elements in Group 18 of the periodic table with full valence electron shells, making them stable and non-reactive. Argon is a noble gas with 8 valence electrons, fulfilling the octet rule. Hydrogen (A) is a nonmetal in Group 1, Fluorine (B) is a halogen in Group 17, and Nitrogen (D) is a nonmetal in Group 15, none of which are noble gases.