HESI A2 Chemistry

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: B

Rationale: The correct answer is B: Alpha, Beta, Gamma. - Alpha radiation consists of helium nuclei. - Beta radiation consists of high-energy electrons or positrons. - Gamma radiation is electromagnetic radiation. Alpha, Beta, and Gamma are the three most common types of radiation in nuclear chemistry. Choice A is incorrect because "Delta" is not a type of radiation in nuclear chemistry. Choice C is incorrect because "Delta" is not a type of radiation, and the order is incorrect. Choice D is incorrect because "Delta" is not a type of radiation, and the order is incorrect.

Correct Answer: A

Rationale: The correct answer is A because the rate of effusion of a gas is inversely proportional to the square root of its molar mass, assuming the same conditions. Since Gas A has twice the mass of Gas B, Gas B will effuse faster. Therefore, you will smell Gas A before you smell Gas B. Choice B is incorrect because Gas B will be smelled first due to its faster effusion rate. Choices C and D are incorrect because both gases will eventually be smelled due to their odorous nature, but the order of detection is based on effusion rates, not presence or absence of smell.

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: Sum of protons and neutrons. Atomic mass is the total mass of an atom, which is the combined mass of protons and neutrons in the nucleus. This value is measured in atomic mass units (amu). Choice A is incorrect because it refers to the atomic number (number of protons). Choice C is incorrect as it only considers the number of neutrons, not the total mass. Choice D is incorrect because atomic mass is not an average weight but a specific value for a single atom.