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: 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.

Correct Answer: D

Rationale: The correct answer is D: Wavefunction. A wavefunction in quantum mechanics is a mathematical function used to describe the behavior of particles, such as electrons, in wave-particle duality. It gives the probability amplitude of finding a particle at a specific position, time, and sometimes spin. The other choices are incorrect because: A: Wavelength is the distance between two consecutive points of a wave with the same phase. B: Frequency is the number of wave cycles passing a point per unit of time. C: Wavenumber is the spatial frequency of a wave, defined as the number of waves per unit distance.

Correct Answer: B

Rationale: Dalton's law states that the total pressure of a mixture of gases is equal to the sum of the partial pressures of the individual gases. In the given equation, Ptot = Pa + Pb, it directly represents Dalton's law where Ptot is the total pressure and Pa and Pb are component pressures. This equation shows that the total pressure is the sum of the pressures contributed by each gas in the mixture. Therefore, choice B is correct. Henry's law deals with the solubility of a gas in a liquid, not the relationship between the total and partial pressures of gases in a mixture (Choice A). Boyle's law relates pressure and volume of a gas at constant temperature, not the total and partial pressures of gases in a mixture (Choice C). Gay-Lussac's law describes the relationship between pressure and temperature of a gas at constant volume, not the total and partial pressures of gases in a mixture (Choice D).