HESI A2 Chemistry Practice Test

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: B

Rationale: The correct answer is B. Temperature affects reaction rates by increasing kinetic energy. Particle size influences surface area available for collision. Concentration impacts frequency of collisions. Catalysts lower activation energy. Barometric pressure, container material, elevation, and volatility do not directly affect reaction rates. Option A includes "barometric pressure" and "facilitator," which are irrelevant. Option C includes "container material" and "elevation," which are not factors. Option D includes "volatility," which is not typically a factor in rates of reaction.

Correct Answer: A

Rationale: The correct answer is A: Brownian motion. This phenomenon was first observed by Robert Brown in 1827. Brownian motion is the random movement of small particles suspended in a liquid, caused by the unbalanced impacts of molecules on the particle. This motion is a result of the constant and random motion of molecules in the liquid colliding with the particle, causing it to move in a zigzag pattern. Grey's kinesis (choice B) and Boyle's wave (choice C) are not valid terms associated with this concept and are therefore incorrect. Choice D (None of the above) is also incorrect as Brownian motion accurately describes the phenomenon described in the question.

Correct Answer: C

Rationale: The statement that the volume of a gas is directly proportional to its absolute temperature at constant pressure aligns with Charles' Law. This law states that for a fixed amount of gas at a constant pressure, the volume of the gas is directly proportional to its absolute temperature. As the temperature increases, the volume of the gas also increases proportionally. This relationship is depicted by the equation V1/T1 = V2/T2. The other choices are incorrect because the Combined Gas Law involves pressure, volume, and temperature changes simultaneously; Boyle's Law describes the inverse relationship between pressure and volume at constant temperature, and the Ideal Gas Law is a combination of Boyle's, Charles', and Avogadro's Laws.

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.