HESI A2 Chemistry

Correct Answer: A

Rationale: The correct answer is A: Zinc sulfate. ZnSO₄ consists of zinc (Zn) and sulfate (SO₄) ions. The name of an ionic compound follows the pattern of cation name + anion name with appropriate suffixes. In this case, "sulfate" is the correct name for the polyatomic ion SO₄, so the compound is named zinc sulfate. Incorrect choices: B: Zinc sulfide - Sulfide is a different anion (S²⁻) than sulfate. C: Zinc sulfur - Incorrect as it doesn't specify the anion involved. D: Zinc oxide - Oxide is a different anion (O²⁻) than sulfate.

Correct Answer: B

Rationale: Failed to generate a rationale after 5 retries.

Correct Answer: C

Rationale: The correct answer is C: Cl and P. Both chlorine (Cl) and phosphorus (P) are in the same group on the periodic table (Group 7A/17) and therefore have similar outer electron configurations. This results in similar reactivity patterns, such as forming covalent compounds. Choices A, B, and D are incorrect because they involve elements from different groups with different electron configurations and reactivity patterns. He (helium) and H (hydrogen) are both in different groups and have very different properties. K (potassium) and Ar (argon) are from different groups and have different reactivity levels. Ba (barium) and Mg (magnesium) are also from different groups and exhibit different reactivity behaviors.

Correct Answer: C

Rationale: To determine the time for the substance to decay to 7 kg, we need to calculate the number of half-lives required. Each half-life reduces the substance by half. Given: Initial mass = 56 kg, Final mass = 7 kg, Half-life = 12 days. Number of half-lives = log(final mass / initial mass) / log(0.5) = log(7/56) / log(0.5) = 3.807 / -0.301 = -12.66. As the number of half-lives must be a whole number, we round up to 13 half-lives. Total time = 13 * 12 days = 156 days. Therefore, the correct answer is C (36 days). The other choices are incorrect because they do not accurately represent the calculation based on the half-life of the substance.

Correct Answer: B

Rationale: The correct answer is B (2). In a single covalent bond, two electrons are shared between two atoms to achieve a stable electron configuration. This sharing of electrons allows both atoms to fill their outermost electron shell and achieve a stable, lower energy state. This sharing of two electrons forms a single covalent bond. Explanation for other choices: A (1): One electron sharing would not be sufficient to form a stable covalent bond. C (3) and D (4): These options are incorrect because a single covalent bond involves the sharing of only two electrons, not three or four.