Chemistry HESI A2 Practice Test

Correct Answer: A

Rationale: The correct answer is A (pH 3) for lemon juice. Lemon juice is acidic due to citric acid content, resulting in a low pH value. The pH scale ranges from 0-14, with 7 being neutral. Lemon juice with a pH of 3 is considered highly acidic. Choice B (pH 5) is less acidic than choice A. Choice C (pH 7) is neutral, which is not characteristic of lemon juice. Choice D (pH 9) is alkaline, opposite to the acidity of lemon juice. Lemon juice's low pH value contributes to its sour taste and preservation properties.

Correct Answer: B

Rationale: The correct answer is B: Semimetals. These elements exhibit properties of both metals and nonmetals. They are also known as metalloids. B, Si, As, Te, At, Ge, and Sb are located along the staircase pattern on the periodic table, indicating their intermediate nature. They have characteristics like both metals (e.g., conductivity) and nonmetals (e.g., brittleness). Choice A (Metals) is incorrect because these elements do not exhibit all typical metal properties. Choice C (Nonmetals) is incorrect because they do not possess all nonmetal properties exclusively. Choice D (Ultrametals) is not a recognized classification in chemistry.

Correct Answer: A

Rationale: To balance the equation, count the number of O atoms on both sides. If the equation is balanced, the coefficient of O should be the same on both sides. In this case, the coefficient of O is already 1 on both sides (since O appears only once on each side), so the correct answer is A. Choices B, C, and D are incorrect because changing the coefficient of O to any of those values would unbalance the equation.

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: C

Rationale: The correct answer is C: Polar covalent and ionic. When an acid reacts with a base, water and a salt are produced. In water, the bonds between hydrogen and oxygen are polar covalent due to the electronegativity difference between the two atoms. In the salt formed, the bond between the cation and anion is ionic, as one atom donates electrons to the other, resulting in a strong electrostatic attraction. Choice A (Liquid and metallic) is incorrect as it does not describe the bonds formed in water and the salt. Choice B (Polar and nonpolar covalent) is incorrect because nonpolar covalent bonds do not form in this scenario. Choice D (Ionic only) is incorrect because water forms polar covalent bonds, in addition to the ionic bonds in the salt.