Chemistry HESI A2 Quizlet

Correct Answer: C

Rationale: Alpha particles are positively charged and relatively large, so they have low penetrating power. A piece of paper can stop alpha particles because the paper's thickness provides enough material for the particles to collide with and lose their energy through ionization. Aluminum foil and glass are not thick enough to effectively stop alpha particles. Plastic, depending on its thickness, may not provide sufficient shielding to stop alpha particles completely. In summary, the correct answer is C because the thickness of a piece of paper is sufficient to stop alpha particles, while the other choices are not adequate for effective shielding.

Correct Answer: B

Rationale: The correct answer is B: Single replacement. In this type of reaction, an active metal replaces another metal in an ionic compound, forming a new compound. This is due to the reactivity of the active metal displacing the less reactive metal in the compound. Combustion (choice A) involves a substance reacting with oxygen to produce heat and light. Synthesis (choice C) is the combination of two or more substances to form a new compound. Decomposition (choice D) is when a compound breaks down into simpler substances. In this scenario, single replacement best fits the description of an active metal reacting with an ionic compound to create a new compound.

Correct Answer: A

Rationale: The Group VIIA elements, also known as the halogens, have a charge of -1. This is because they require one additional electron to achieve a stable octet configuration, making them highly reactive nonmetals. The correct answer is A (-1) because halogens readily gain one electron to fill their outer energy level. Choices B (-2) and D (1) are incorrect because the charge of Group VIIA elements is typically -1, not -2 or +1. Choice C (0) is incorrect because Group VIIA elements do not have a charge of 0; they have a tendency to gain an electron rather than lose one.

Correct Answer: B

Rationale: Increasing the concentration of reactants increases the chances of reactant molecules colliding, leading to more successful collisions and higher reaction rate. This is explained by the collision theory in chemistry. Choice A is incorrect because increasing concentration typically increases the reaction rate. Choice C is incorrect as increasing concentration does not stop the reaction, but rather can enhance it. Choice D is also incorrect as concentration of reactants has a direct impact on reaction rate.

Correct Answer: D

Rationale: Dispersion forces are the weakest intermolecular force because they are caused by temporary fluctuations in electron distribution, leading to temporary dipoles. These forces exist between all molecules, regardless of polarity. Dipole interactions are stronger as they involve permanent dipoles in polar molecules. Hydrogen bonding is even stronger, occurring between a hydrogen atom bonded to a highly electronegative atom and another electronegative atom. Van der Waals forces encompass both dipole interactions and dispersion forces. Thus, dispersion forces are the weakest intermolecular force among the given options.