HESI A2 Chemistry Questions

Correct Answer: B

Rationale: The correct answer is B: Oxygen. During photosynthesis, plants use carbon dioxide and water to produce glucose and oxygen. Oxygen is released as a byproduct of this process through the stomata in plant leaves. Carbon dioxide (A) is actually used up during photosynthesis, not released. Nitrogen (C) and Helium (D) are not involved in the process of photosynthesis.

Correct Answer: A

Rationale: The correct answer is A: Covalent bond. In a covalent bond, two atoms share electrons to complete their outer electron shells and achieve stability. This sharing results in a strong bond between the atoms. Ionic bonds involve the transfer of electrons, metallic bonds involve a "sea" of shared electrons in a metal lattice, and hydrogen bonds are weaker interactions between a hydrogen atom and an electronegative atom. Covalent bonds are the only option where electrons are shared between atoms to form a stable bond.

Correct Answer: B

Rationale: The correct answer is B: To speed up reactions. Enzymes work by lowering the activation energy required for a reaction to occur, thereby speeding up the reaction without being consumed in the process. This allows reactions to occur at a faster rate than they would without the enzyme. Enzymes do not provide energy (choice A) but rather facilitate energy transfer during reactions. While enzymes decrease activation energy (choice C), this is a means to speed up reactions rather than their primary function. Enzymes act as catalysts (choice D) by increasing the rate of reactions, making them an essential component in biochemical processes.

Correct Answer: A

Rationale: The correct answer is A: Hydrogen acceptors. Bases or alkaline solutions are known as hydrogen acceptors because they can accept a hydrogen ion (H+) to form water. This process is known as neutralization. Choices B and C are incorrect because alkaline solutions are not solutions of low pH or hydrogen donors. Choice D, amphoteric, refers to substances that can act as both acids and bases, which is not the definition of bases or alkaline solutions.

Correct Answer: D

Rationale: The correct answer is D: hydriodic acid. In aqueous solution, HI dissociates into H+ and I- ions, forming hydriodic acid. Choice A (hydroiodic acid) is incorrect as it does not reflect the presence of water in the compound. Choice B (hydrogen monoiodide) is incorrect as it incorrectly implies the presence of only one iodide ion. Choice C (hydrogen iodide) is incorrect as it does not specify the compound in aqueous solution. Therefore, the correct term for aqueous HI is hydriodic acid.