HESI A2 Chemistry

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: 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: Butane. In this compound, CH₃-CH₂-CH₂-CH₃, there are four carbon atoms connected in a straight chain, making it a butane. The prefix "but-" indicates that there are four carbon atoms, and the suffix "-ane" indicates that the compound contains only single bonds between the carbon atoms. Therefore, the correct name is Butane. Choice A: Cyclobutane is incorrect because it would be a cyclic compound with four carbon atoms forming a ring. Choice C: Butene is incorrect because it would have a double bond between two carbon atoms, making it an alkene. Choice D: Butyne is incorrect because it would have a triple bond between two carbon atoms, making it an alkyne.

Correct Answer: C

Rationale: The correct answer is C: Between 6 and 8. Tap water is typically slightly alkaline, with a pH range between 6.5 and 8.5. This is considered neutral to slightly basic, as pure water has a pH of 7. The pH scale ranges from 0 to 14, with 7 being neutral. Choices A, B, and D are incorrect because tap water is not highly acidic (A), acidic (B), or highly alkaline (D). Tap water falls within the slightly basic range on the pH scale.

Correct Answer: B

Rationale: The correct answer is B: Beta radiation. Beta radiation consists of high-energy electrons or positrons traveling at high speeds, typically around 16,000 km/sec. This is because beta particles are emitted during the decay of a radioactive nucleus when a neutron changes into a proton and an electron (beta-minus decay) or a proton changes into a neutron and a positron (beta-plus decay). Alpha radiation (A) consists of helium nuclei, gamma radiation (C) is high-energy electromagnetic radiation, and there is no such thing as delta radiation (D) in the context of nuclear physics.