Chemistry HESI A2 Practice Test

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: C

Rationale: The correct answer is C: Number of neutrons. Isotopes have the same number of protons (same atomic number), but different numbers of neutrons (different mass numbers). Carbon-12 and carbon-14 both have 6 protons (atomic number for carbon), but carbon-12 has 6 neutrons while carbon-14 has 8 neutrons. Therefore, the common trait between isotopes is the number of neutrons. Explanation for why other choices are incorrect: A: Number of nuclear particles - Isotopes have different numbers of neutrons, so they do not have the same number of nuclear particles. B: Number of protons - Isotopes have the same number of protons, but different numbers of neutrons. D: Mass number - Isotopes have different mass numbers due to differing numbers of neutrons, so this is not the common trait between isotopes.

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: B

Rationale: The correct answer is B: Anion. When an atom gains one or more electrons, it becomes negatively charged, forming an anion. This process is known as gaining electron(s) to achieve a stable electron configuration. A cation (A) is formed when an atom loses electron(s) and becomes positively charged. Isotope (C) refers to atoms of the same element with different numbers of neutrons. Electron (D) is a fundamental subatomic particle, not a term for an atom gaining electrons.