Chemistry HESI A2 Practice Test

Correct Answer: D

Rationale: The correct answer is D: Crystalline shape. Ionic compounds have a regular, repeating arrangement of ions in a crystal lattice structure due to strong electrostatic forces between oppositely charged ions. This leads to the formation of distinct geometric shapes, known as crystalline shapes. Choice A is incorrect because ionic compounds typically have high melting points due to strong ionic bonds. Choice B is incorrect as ionic compounds are good conductors when dissolved in water or in a molten state. Choice C is incorrect because ionic compounds involve transfer, not sharing, of electrons between ions.

Correct Answer: B

Rationale: Failed to generate a rationale after 5 retries.

Correct Answer: A

Rationale: The correct answer is A because the rate of diffusion is inversely proportional to the square root of the molar mass. Therefore, if gas A has four times the molar mass of gas B, gas A would diffuse at half the rate of gas B. This is because the square root of 4 is 2, indicating that gas A would diffuse at a rate that is half of gas B. Choice B is incorrect because if gas A has four times the molar mass of gas B, it would not diffuse at twice the rate of gas B. Choice C is incorrect because gas A would not diffuse at a quarter the rate of gas B. Choice D is incorrect because gas A would not diffuse at four times the rate of gas B.

Correct Answer: D

Rationale: The correct answer is D: Xe. Xenon (Xe) is a noble gas, meaning it has a full outer electron shell, making it highly stable and least likely to react with other elements. Li (A) is a highly reactive alkali metal, Cr (B) is a transition metal with varying reactivities, and Nd (C) is a rare-earth metal that can exhibit reactivity. In summary, Xe is the least reactive as noble gases tend to be chemically inert due to their stable electron configuration.

Correct Answer: A

Rationale: The correct answer is A. Amino acids typically contain an amine group (R-NH2) and a carboxylic acid group (R-COOH). The amine group acts as a base, accepting protons, while the carboxylic acid group acts as an acid, donating protons. This combination allows amino acids to participate in acid-base reactions and form peptide bonds in proteins. Choice B is incorrect because R-CHO is an aldehyde group, not typically found in amino acids. Choice C is incorrect because R-OH is a hydroxyl group and R-COOR is an ester group, neither of which are characteristic functional groups of amino acids. Choice D is incorrect as R-O-R is an ether group, not commonly present in amino acids, and R-COOH alone is not sufficient as amino acids also require an amine group.