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: 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: 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: 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: C

Rationale: The correct answer is C: Electrons. Electrons are negatively charged subatomic particles found in the electron cloud surrounding the nucleus of an atom. They are responsible for chemical bonding and electricity conduction. Protons (A) are positively charged, neutrons (B) are neutral, and isotopes (D) are atoms with the same number of protons but different number of neutrons.