HESI A2 Chemistry Questions

Correct Answer: A

Rationale: Acids have a sour taste due to their ability to release hydrogen ions (H+) in solution. This sour taste is a key characteristic property of acids. Bitter taste (Choice B) is associated with bases, not acids. Reacting with bases (Choice C) is a general property of acids, not a characteristic property. Slippery feel (Choice D) is an attribute of bases, not acids. Thus, the correct answer is A because of the unique sour taste exhibited by acids.

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: Fluorine. Halogens are a group of elements in the periodic table that include Fluorine, Chlorine, Bromine, Iodine, and Astatine. They are highly reactive nonmetals with seven valence electrons, making them very electronegative. Fluorine specifically is the most reactive and electronegative element, commonly found in compounds like fluoride toothpaste. A: Oxygen is not a halogen. It is a nonmetal but belongs to the chalcogen group in the periodic table. C: Sodium is a metal and belongs to the alkali metal group, not a halogen. D: Carbon is a nonmetal but is not a halogen. It belongs to the p-block elements on the periodic table.

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.

Correct Answer: A

Rationale: The correct answer is A: Synthesis reaction. In a synthesis reaction, two or more reactants combine to form a single product. This type of reaction is characterized by the formation of a more complex molecule from simpler ones. The other choices are incorrect because: B: Combustion reaction involves the rapid combination of a substance with oxygen, producing heat and light. C: Decomposition reaction involves the breakdown of a compound into simpler substances. D: Double displacement reaction involves the exchange of ions between two compounds to form two new compounds.