Chemistry HESI A2 Practice Test

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: C

Rationale: The correct answer is C: Fluorine. Fluorine is not an allotrope of carbon because allotropes are different forms of the same element. Fluorine is a different element altogether. Diamond, graphite, and buckminsterfullerene are all allotropes of carbon, each with unique molecular structures and properties. Diamond has a tetrahedral structure, graphite has layers of hexagonal rings, and buckminsterfullerene has a spherical shape. Fluorine, on the other hand, is a diatomic molecule consisting of two atoms of fluorine bonded together. Therefore, C is the correct answer as it does not belong to the category of carbon allotropes.

Correct Answer: D

Rationale: The correct answer is D: OH⁻. In water solutions of bases, OH⁻ ions are dominant as they are responsible for the basic properties. Bases release OH⁻ ions when dissolved in water, leading to an increase in pH. MgCl₂ and 2HCl do not contribute to basicity as they do not release OH⁻ ions. H⁺ ions, found in strong acids, are associated with acidic properties and would not dominate in a base solution.

Correct Answer: A

Rationale: Failed to generate a rationale after 5 retries.

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.