HESI A2 Chemistry

Correct Answer: B

Rationale: The correct answer is B: 19 protons. Potassium's atomic number is 19, which represents the number of protons in its nucleus. Protons are positively charged particles in an atom. Option A (18) is incorrect as it does not match the atomic number of Potassium. Options C (20) and D (21) are also incorrect as they do not correspond to Potassium's atomic number. Thus, the correct answer is B (19) based on the periodic table.

Correct Answer: B

Rationale: Failed to generate a rationale after 5 retries.

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: 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: B

Rationale: The correct answer is B: Acid. Acids are hydrogen or proton donors, corrosive to metals, turn blue litmus paper red (indicating acidity), and become less acidic when mixed with a base due to neutralization reaction. Bases (choice A) are proton acceptors and do not exhibit these characteristics. Salts (choice C) are formed from the reaction between an acid and a base and do not fit all the given criteria. Hydroxides (choice D) are bases and do not donate protons or exhibit the acidic properties described.