HESI A2 Chemistry Practice Test

Correct Answer: C

Rationale: The correct answer is C: Ionic bonds. When elements with low electronegativity (almost empty outer shells) react with elements with high electronegativity (mostly full outer shells), they transfer electrons, leading to the formation of ionic bonds. In ionic bonds, electrons are completely transferred from one element to another, creating positively and negatively charged ions that are attracted to each other due to electrostatic forces. Explanation of other choices: A: Hydrogen bonds are formed between a hydrogen atom and a highly electronegative atom like oxygen or nitrogen. They are not formed by the transfer of electrons, unlike in ionic bonds. B: Covalent bonds involve the sharing of electrons between atoms, rather than the transfer of electrons as in ionic bonds. D: Nuclear bonds refer to the forces that hold the protons and neutrons together in the nucleus of an atom, not related to the transfer of electrons in chemical bonding.

Correct Answer: C

Rationale: Henry's Law states that the solubility of a gas in a liquid is directly proportional to the partial pressure of the gas above the liquid (P = kC). This means that as the partial pressure of the gas increases, the amount of gas that dissolves in the liquid also increases. This relationship is specifically for gases and volatile substances in liquids. Boyle's Law relates pressure and volume, Gay-Lussac's Law relates pressure and temperature, and Charles' Law relates volume and temperature. Therefore, the correct answer is C, Henry's Law, because it directly describes the relationship between gas solubility and partial pressure.

Correct Answer: D

Rationale: The correct answer is D, the law of constant composition. This law states that a compound always contains the same elements in the same proportion by mass. In the case of water, the ratio of hydrogen to oxygen by mass is always 1:8, regardless of the source or quantity of water. This is a key principle in chemistry and helps identify and characterize different compounds. A: The law of multiple proportions deals with the ratios of different elements that can combine to form different compounds, not the same compound. B: The law of conservation of mass states that mass is neither created nor destroyed in a chemical reaction. C: The law of conservation of energy states that energy cannot be created or destroyed, but this is not directly related to the composition of compounds.

Correct Answer: B

Rationale: The correct answer is B because glycogen is a type of starch that is primarily found in animals, particularly in their liver and muscles, serving as a storage form of glucose. Plant starches (choice A) are primarily found in plants, not animals. Glucose (choice C) is a simple sugar molecule, not a type of starch. Cellulose (choice D) is a structural polysaccharide found in plant cell walls, not a storage form of glucose like glycogen. Therefore, the correct answer is B, as glycogen is indeed an animal starch.

Correct Answer: A

Rationale: The correct answer is A: Protons. Isotopes of an element have the same number of protons, as the number of protons determines the element's identity. Isotopes differ in the number of neutrons, leading to variations in atomic mass. Neutrons play a role in the stability and mass of an isotope but do not affect the element's identity. Protons and electrons determine the overall charge of an atom, but isotopes only vary in the number of neutrons, not electrons. Thus, the correct answer is A as it aligns with the fundamental concept of isotopes having the same number of protons.