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: 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: Correct Answer: A Rationale: 1. pH is a measure of hydrogen ion concentration in a solution. 2. The formula for pH is pH = - log[H+]. 3. This formula indicates an inverse logarithmic relationship between pH and H+ concentration. 4. The effective concentration of hydrogen ions directly influences pH. 5. The molarity of H+ ions is crucial in determining the pH value of a solution. Summary: Choice A is correct as it accurately describes the relationship between pH and hydrogen ion concentration, supported by the logarithmic formula. Choices B, C, and D are incorrect as they misinterpret the role of pH and its relationship to hydrogen ions in a solution.

Correct Answer: C

Rationale: The correct answer is C: Boyle. Boyle's Law states that the pressure and volume of a gas are inversely proportional when temperature is constant. Boyle conducted experiments that led to this discovery. Choice A, Charles, is known for Charles's Law which relates volume and temperature. Choice B, Combine, is not a known scientist. Choice D, Gay-Lussac, is known for Gay-Lussac's Law which relates pressure and temperature.

Correct Answer: B

Rationale: The typical oxidation state of oxygen in most compounds is -2. Oxygen is highly electronegative and tends to gain 2 electrons to achieve a stable octet configuration. This results in an oxidation state of -2 in compounds like water (H2O) and carbon dioxide (CO2). Therefore, choice B is correct. Choice A (-1) is incorrect because oxygen rarely has an oxidation state of -1 in compounds. Choice C (0) is incorrect as oxygen doesn't usually have an oxidation state of 0; it prefers to gain electrons. Choice D (-3) is incorrect as it is an uncommon oxidation state for oxygen in compounds.