HESI A2 Chemistry Practice Test

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: C

Rationale: The correct answer is C: Chemical bonds. Chemical bonds encompass both ionic and covalent bonds, making them an intermediate between the extremes represented by these two types of bonds. Ionic bonds involve complete transfer of electrons, while covalent bonds involve sharing of electrons. Therefore, chemical bonds, which encompass both types, are the most appropriate choice. Summary: A: Ionic bonds - involve complete transfer of electrons, not an intermediate between extremes. B: Covalent bonds - involve sharing of electrons, not an intermediate between extremes. D: Polar bonds - a specific type of covalent bond, not representing the intermediate nature of chemical bonds.

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.

Correct Answer: C

Rationale: The correct answer is C: Frequency. Frequency is defined as the number of cycles of a wave that move past a fixed observation point per second. It is measured in Hertz (Hz). Frequency determines the pitch of a sound wave and the color of light. Choice A, Wave, is the general term for a disturbance that travels through a medium. Choice B, Wavelength, is the distance between two consecutive points on a wave that are in phase. Choice D, Wavefunction, is a mathematical function that describes the wave-like behavior of a particle in quantum mechanics.

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.