Chemistry HESI A2 Quizlet

Correct Answer: B

Rationale: The correct answer is B, the Law of Conservation of Mass. This law states that matter cannot be created or destroyed in a chemical reaction, only rearranged. This is based on the principle of mass conservation, where the total mass of the reactants equals the total mass of the products. This law is supported by experimental evidence and is a fundamental principle in chemistry. Choice A, the Law of Conservation of Energy, is incorrect because it pertains to the conservation of energy, not mass. Choice C, the Law of Constant Composition, is incorrect as it refers to compounds having fixed ratios of elements. Choice D, the Law of Multiple Proportions, is incorrect because it describes the ratios in which elements combine to form different compounds, not the conservation of mass.

Correct Answer: B

Rationale: Stoichiometry is the study of mass relationships in chemical reactions. It involves calculating the quantities of reactants and products. By using balanced chemical equations, one can determine the amounts of substances involved. This answer is correct because it directly relates to the main concept of stoichiometry. Explanation for other choices: A: The study of energy changes in chemical reactions - This is incorrect as it refers to the field of thermodynamics. C: The study of atomic structure - This is incorrect as it pertains to atomic theory and not the mass relationships in reactions. D: The study of molecular geometry - This is incorrect as it deals with the spatial arrangement of atoms in molecules, not the mass relationships in reactions.

Correct Answer: A

Rationale: The Group IA elements, also known as alkali metals, have a +1 charge. This is because they have one valence electron, which they readily lose to achieve a stable electron configuration. This results in them forming ions with a +1 charge. Therefore, the correct answer is A. Choice B (+2) is incorrect because alkali metals do not typically form ions with a +2 charge due to their tendency to lose only one electron. Choice C (+3) is also incorrect as alkali metals do not form ions with a +3 charge. Choice D (0) is incorrect because alkali metals are known for their tendency to lose electrons to achieve a stable configuration, resulting in a positive charge.

Correct Answer: B

Rationale: The correct answer is B: Physical. When no change is made to the chemical composition of a substance, it indicates a physical change. In physical changes, the substance retains its chemical identity and only its physical properties, such as shape, size, and state, are altered. This is because the particles in the substance rearrange or move without forming new substances. Choice A (Chemical) involves a change in the chemical composition, so it is incorrect. Choice C (Nuclear) involves changes at the atomic level, leading to different elements, which is not the case here. Choice D (Mechanical) involves changes in position and motion of objects, not relevant to the chemical composition of a substance.

Correct Answer: B

Rationale: The sum of protons and neutrons in an element represents the mass number. Protons and neutrons are located in the nucleus and contribute to the mass of an atom. The atomic number (A) is the number of protons in an atom, not the sum of protons and neutrons. Atomic mass (C) is the average mass of an element's isotopes, considering their abundance, and is not the sum of protons and neutrons. Neutron number (D) refers to the specific number of neutrons in an atom, not the total mass of the nucleus. Therefore, the correct answer is B, as it accurately represents the total mass of an atom.