HESI A2 Chemistry Questions

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: B

Rationale: The correct answer is B: Halogens. Halogens are a group of elements in Group 17 of the periodic table, including chlorine, fluorine, and iodine. They are known for their high reactivity and tendency to form salts with metals. Alkali metals (A) are in Group 1, transition metals (C) are in the middle part of the periodic table, and noble gases (D) are in Group 18. These choices are incorrect as they do not include chlorine, fluorine, and iodine, which are characteristic of the halogens.

Correct Answer: B

Rationale: The correct answer is B: Na. Sodium's chemical symbol is Na because it is derived from its Latin name "natrium." N represents nitrogen, Cl represents chlorine, and H represents hydrogen, making them incorrect choices. Remember to consider the element's name origins for accurate symbol identification.

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: B

Rationale: The correct answer is B: It releases heat. In an exothermic reaction, energy is released in the form of heat to the surroundings. This results in a temperature increase in the surrounding environment. The other choices are incorrect because: A: It absorbs heat - This is a characteristic of an endothermic reaction, where heat is absorbed from the surroundings. C: It remains neutral - This does not describe the nature of an exothermic reaction, which involves the release of heat. D: It requires energy input - This is more in line with an endothermic reaction, where energy input is needed to drive the reaction.