HESI A2 Chemistry Practice Test

Correct Answer: A

Rationale: Rationale: A is false because in an endothermic process, solubility usually increases with increasing temperature and decreases with decreasing temperature due to the absorption of heat. B is true, as solubility generally decreases with increasing temperature in exothermic processes. C and D are incorrect as A is false.

Correct Answer: B

Rationale: The correct answer is B: 6. In sulfuric acid (H2SO4), the oxidation states of hydrogen and oxygen are always +1 and -2, respectively. Since the overall charge of the molecule is 0, the sum of the oxidation states must equal 0. Given that there are two hydrogen atoms (each with an oxidation state of +1) and four oxygen atoms (each with an oxidation state of -2), the oxidation state of sulfur (S) can be calculated as follows: 2(+1) + x + 4(-2) = 0. Solving for x gives x = +6, indicating that the oxidation state of the sulfur atom in sulfuric acid is indeed +6. Summary: A: 4 - Incorrect. This value does not account for the correct oxidation state calculation in sulfuric acid. C: 8 - Incorrect. This value is too high and does not align with the correct oxidation state calculation. D:

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.

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: D

Rationale: Rationale: 1. Wavelength is defined as the distance between adjacent peaks or troughs on a wave. 2. Frequency is the number of wave cycles per unit time, not the distance between peaks/troughs. 3. Wavenumber is the spatial frequency of a wave, not the distance between peaks/troughs. 4. Wave oscillation refers to the movement of particles in a wave, not the distance between peaks/troughs. Summary: The correct answer is D because wavelength specifically refers to the distance between adjacent peaks or troughs on a wave, whereas the other choices are related to different properties of waves.