HESI A2 Chemistry Questions

Correct Answer: A

Rationale: The correct answer is A: Synthesis reaction. In a synthesis reaction, two or more reactants combine to form a single product. This type of reaction is characterized by the formation of a more complex molecule from simpler ones. The other choices are incorrect because: B: Combustion reaction involves the rapid combination of a substance with oxygen, producing heat and light. C: Decomposition reaction involves the breakdown of a compound into simpler substances. D: Double displacement reaction involves the exchange of ions between two compounds to form two new compounds.

Correct Answer: A

Rationale: The correct answer is A: 7. In a neutral solution, the concentration of H+ ions equals the concentration of OH- ions, resulting in a pH of 7. This signifies a balance between acidity and alkalinity. Choice B (0) is incorrect as it represents a strong acid, choice C (14) is incorrect as it represents a strong base, and choice D (4) is incorrect as it indicates an acidic solution.

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: Uranium. Uranium has the highest atomic number among the options provided. Atomic number represents the number of protons in the nucleus of an atom. Uranium has an atomic number of 92, which is higher than the other elements listed. Hydrogen has an atomic number of 1, Radon has an atomic number of 86, and Bismuth has an atomic number of 83. Therefore, Uranium has the highest atomic number, making it the correct choice.

Correct Answer: B

Rationale: The correct answer is B: Solid. In solids, particles are tightly packed in a fixed position due to strong intermolecular forces holding them in place. This results in a definite shape and volume. In liquids (choice A), particles are close together but not in fixed positions, allowing them to flow and take the shape of their container. In gases (choice C), particles are far apart and move freely, leading to indefinite shape and volume. In plasma (choice D), particles are highly energized, ionized, and not bound together, making them not tightly packed or in fixed positions.