HESI A2 Chemistry

Correct Answer: C

Rationale: The correct answer is C: A 5 carbon sugar. Pentose sugars are carbohydrates with 5 carbon atoms. They are essential components of nucleic acids like DNA and RNA. A is incorrect because it has 6 carbons, not 5. B is incorrect as it has 4 carbons. D is incorrect as it has 7 carbons, not 5. Therefore, the correct choice is C as it accurately describes a pentose sugar.

Correct Answer: C

Rationale: The molar mass of sodium chloride (NaCl) is calculated by adding the atomic masses of sodium (Na) and chlorine (Cl) together. Sodium has an atomic mass of approximately 23 g/mol, and chlorine has an atomic mass of approximately 35.5 g/mol. Adding these two values gives a molar mass of 58.5 g/mol for sodium chloride. Rounding to the nearest whole number, the mass of one mole of sodium chloride is 58 g/mol, which corresponds to choice C. Choices A, B, and D are incorrect as they do not accurately reflect the molar mass of sodium chloride. Option A is close but slightly lower than the correct value, while options B and D are significantly off.

Correct Answer: C

Rationale: Step-by-step rationale: 1. Nonmetals are elements that lack metallic properties. 2. Sulfur is a nonmetal as it exists in a gaseous form at room temperature, lacks luster, and is a poor conductor of heat and electricity. 3. Mercury (A) is a metal as it is a liquid at room temperature. 4. Magnesium (B) and Potassium (D) are both metals as they are solid at room temperature and exhibit typical metallic properties. Summary: - A: Mercury is a metal. - B: Magnesium is a metal. - C: Sulfur is the correct answer as a nonmetal. - D: Potassium is a metal.

Correct Answer: A

Rationale: To find molarity, divide moles of solute by liters of solution. In this case, molarity = 45 moles NaCl / 4 L = 11.25 M. However, NaCl is a salt, so you need to consider its formula weight (58.44 g/mol). Thus, 45 moles NaCl is 45 moles x 58.44 g/mol = 2634.6 g. Convert grams to kilograms (2634.6 g / 1000 = 2.6346 kg). Finally, molarity = 2.6346 kg / 4 L = 0.11 M NaCl. Choice A is correct because it accurately calculates the molarity. Choices B, C, and D are incorrect due to incorrect calculations.

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.