HESI A2 Chemistry Questions

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.

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: B

Rationale: The correct answer is B: joule. Joule is the SI unit of energy, defined as the work done when a force of one newton is applied over a distance of one meter. Ohm (A) is the SI unit of electrical resistance, henry (C) is the SI unit of inductance, and newton (D) is the SI unit of force. Therefore, the correct choice is B as it specifically represents energy in the SI system.

Correct Answer: B

Rationale: The correct answer is B: Na. Sodium's chemical symbol is Na because it is derived from its Latin name "natrium." N represents nitrogen, Cl represents chlorine, and H represents hydrogen, making them incorrect choices. Remember to consider the element's name origins for accurate symbol identification.