HESI A2 Chemistry Questions

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: Production of gas. In a chemical change, new substances are formed with different properties. The production of gas is a sign of a chemical reaction due to the formation of new molecules. Choices A, C, and D are physical changes, not chemical changes. A change in shape (A) is a physical change as it does not alter the chemical composition. Melting (C) and freezing (D) are also physical changes, involving the state of matter without changing the chemical composition.

Correct Answer: B

Rationale: The correct answer is B: Neon. Noble gases are a group of elements that are inert and have a full outer electron shell, making them stable and unreactive. Neon belongs to the noble gas group in the periodic table, with a full outer electron shell, making it stable. Oxygen (A) is a reactive nonmetal, hydrogen (C) is a nonmetal but not a noble gas, and argon (D) is also a noble gas but not the correct answer in this case.

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: Carbon dioxide. When an acid reacts with a carbonate, it produces carbon dioxide gas due to the chemical reaction. The acid donates hydrogen ions to the carbonate, forming carbonic acid, which then breaks down into water and carbon dioxide. Oxygen (B), hydrogen (C), and nitrogen (D) are not produced during this specific reaction and are not part of the chemical equation for the reaction between an acid and a carbonate.