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: A

Rationale: The mass number is the sum of protons and neutrons in an atom. Given 6 protons and 6 neutrons, the mass number would be 6+6=12. Electrons do not contribute significantly to the mass number. Therefore, the correct answer is A: 12. Choice B is incorrect as it adds the protons, neutrons, and electrons together. Choice C only considers the number of protons. Choice D is incorrect as it only includes the number of protons.

Correct Answer: B

Rationale: The correct answer is B: Iron. The chemical symbol 'Fe' represents the element iron in the periodic table. Iron is a transition metal with atomic number 26. It is commonly used in construction, manufacturing, and as a vital nutrient in the human body. Lead (choice A), Silver (choice C), and Copper (choice D) have the chemical symbols 'Pb', 'Ag', and 'Cu' respectively, making them incorrect choices. By knowing the periodic table and corresponding chemical symbols, we can easily identify the correct element.

Correct Answer: D

Rationale: The correct answer is D: High specific heat. Water's ability to form hydrogen bonds allows it to absorb and retain a significant amount of heat before its temperature changes. This property is essential for regulating temperature in living organisms and maintaining stable environments. A: Lack of cohesiveness - This is incorrect because water's hydrogen bonding actually promotes cohesion, leading to high surface tension. B: Low surface tension - This is incorrect because water's hydrogen bonding contributes to high surface tension. C: Use as a nonpolar solvent - This is incorrect because water is a polar solvent, not nonpolar, due to its hydrogen bonding capabilities.

Correct Answer: B

Rationale: The correct answer is B: joule. Joule is the SI unit of energy, defined as the work done when a force of one newton is applied over a distance of one meter. Ohm (A) is the SI unit of electrical resistance, henry (C) is the SI unit of inductance, and newton (D) is the SI unit of force. Therefore, the correct choice is B as it specifically represents energy in the SI system.