HESI A2 Chemistry

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: 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.

Correct Answer: D

Rationale: The correct answer is D: W (tungsten). Tungsten has the greatest atomic mass among the elements listed. Tungsten has an atomic number of 74, which corresponds to an atomic mass of approximately 183.84 g/mol. Gold (Au) has an atomic number of 79, with an atomic mass of around 196.97 g/mol, making it heavier than barium (Ba) and iodine (I). Barium has an atomic number of 56, with an atomic mass of about 137.33 g/mol, and iodine has an atomic number of 53, with an atomic mass of roughly 126.90 g/mol. Therefore, tungsten (W) has the greatest atomic mass compared to the other elements listed.

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.

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.