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: A

Rationale: The mass number is the sum of protons and neutrons in an atom. Given 6 protons and 6 neutrons, the mass number would be 6+6=12. Electrons do not contribute significantly to the mass number. Therefore, the correct answer is A: 12. Choice B is incorrect as it adds the protons, neutrons, and electrons together. Choice C only considers the number of protons. Choice D is incorrect as it only includes the number of protons.

Correct Answer: A

Rationale: The correct answer is A: boron. Diatomic molecules consist of two atoms of the same element bonded together. Boron exists as a monatomic element, meaning it exists as single atoms. Fluorine, oxygen, and nitrogen exist naturally as diatomic molecules (F2, O2, N2) due to their stability when bonded together. Boron does not form diatomic molecules because it is less stable in that form.

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: A

Rationale: The correct answer is A: Uranium. Uranium has the highest atomic number among the options provided. Atomic number represents the number of protons in the nucleus of an atom. Uranium has an atomic number of 92, which is higher than the other elements listed. Hydrogen has an atomic number of 1, Radon has an atomic number of 86, and Bismuth has an atomic number of 83. Therefore, Uranium has the highest atomic number, making it the correct choice.