Chemistry HESI A2 Practice Test

Correct Answer: B

Rationale: The correct formula for silver hydroxide is AgOH. Silver is a transition metal with a +1 charge, and hydroxide is OH⁻. To balance the charges, one silver ion combines with one hydroxide ion to form AgOH. Choice A (AgO) is incorrect because it does not include the hydroxide ion. Choice C (AgH) is incorrect as it suggests silver bonding with hydrogen, which is not the case. Choice D (AgH₂O) is incorrect as it implies silver bonding with water molecules, which is not the formula for silver hydroxide.

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: 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.

Correct Answer: B

Rationale: The correct answer is B: Days-long. Medical isotopes used in medicine typically have a short half-life to minimize radiation exposure to patients. A days-long half-life strikes a balance between decay rate and practical usability in medical procedures. Choice A (Seconds-long) would be too short for practical use. Choices C (Years-long) and D (Many years long) would result in prolonged radiation exposure, increasing health risks for patients.

Correct Answer: B

Rationale: The correct answer is B: -1. In HCl, hydrogen is always assigned an oxidation state of +1. Since the overall charge of HCl is 0, the oxidation state of chlorine must be -1 to balance the charge. Chlorine is more electronegative than hydrogen and tends to gain an electron in this compound. Therefore, the oxidation state of the chlorine atom in HCl is -1. Choice A: +1 - Hydrogen is always assigned an oxidation state of +1 in compounds. Choice C: +2 - Chlorine does not have an oxidation state of +2 in HCl. Choice D: -2 - Chlorine's oxidation state is not -2 in HCl.