Chemistry HESI A2 Quizlet

Correct Answer: C

Rationale: The correct answer is C: Combustion. Combustion is a chemical reaction where a compound reacts with oxygen to produce heat, light, and often carbon dioxide and water. In this type of reaction, oxygen is a reactant and typically a hydrocarbon or organic compound is the fuel. Decomposition involves a compound breaking down into simpler substances, synthesis is when two or more substances combine to form a more complex compound, and single replacement is when one element replaces another in a compound. Combustion specifically involves the reaction with oxygen, making it the correct choice in this scenario.

Correct Answer: A

Rationale: The correct answer is A: Enzyme. Enzymes can act as catalysts in chemical reactions by lowering the activation energy required for the reaction to occur, thereby speeding up the reaction without being consumed in the process. Enzymes are biological molecules that are highly specific to their substrates and can facilitate a wide range of chemical reactions. Explanation for why the other choices are incorrect: B: Light - Light can initiate certain chemical reactions by providing energy, but it is not a catalyst as it is not directly involved in lowering the activation energy. C: Water - Water can be a solvent or participate in chemical reactions, but it does not act as a catalyst by lowering activation energy. D: Metal - Some metals can act as catalysts in certain reactions, but not all metals have catalytic properties, and they do not have the same specificity and efficiency as enzymes in biological systems.

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: 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: C

Rationale: The correct answer is C: Anions. Negatively charged ions are referred to as anions because they have gained extra electrons, resulting in a negative charge. Neutrons (A) are neutral particles found in the nucleus of an atom. Protons (B) are positively charged particles found in the nucleus. Cations (D) are positively charged ions that have lost electrons. Therefore, based on the definition of negatively charged ions, anions are the correct choice.