HESI A2 Chemistry Practice Test

Correct Answer: B

Rationale: The correct answer is B: Hydrogen bonds. Hydrogen bonds are formed between a hydrogen atom in a polar covalent bond and a highly electronegative atom like oxygen or nitrogen. In water, hydrogen bonds contribute to its high boiling point, surface tension, and density anomalies. In DNA, hydrogen bonds between base pairs help maintain the double helix structure. Incorrect choices: A: Oxygen links - This is not a recognized term in chemistry and does not accurately describe the type of bonds discussed. C: Dipolar bonds - While dipole-dipole interactions are involved in hydrogen bonding, the term "dipolar bonds" is not commonly used to refer to this specific type of bond. D: N/A - This choice does not provide any information related to the question and is not a valid option.

Correct Answer: C

Rationale: Henry's Law states that the solubility of a gas in a liquid is directly proportional to the partial pressure of the gas above the liquid (P = kC). This means that as the partial pressure of the gas increases, the amount of gas that dissolves in the liquid also increases. This relationship is specifically for gases and volatile substances in liquids. Boyle's Law relates pressure and volume, Gay-Lussac's Law relates pressure and temperature, and Charles' Law relates volume and temperature. Therefore, the correct answer is C, Henry's Law, because it directly describes the relationship between gas solubility and partial pressure.

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: A

Rationale: The correct answer is A: Order of increasing atomic number. This is because the periodic table is arranged based on the number of protons in the nucleus of an atom, which is the atomic number. This arrangement helps in organizing elements based on their properties and allows us to predict the behavior of elements. Choice B (Alphabetical order) is incorrect because elements are not arranged alphabetically but based on their atomic number. Choice C (Order of increasing metallic properties) is incorrect because while elements are grouped based on similar properties, the overall arrangement is not solely based on metallic properties. Choice D (Order of increasing neutron content) is incorrect as the periodic table is based on atomic number (number of protons), not neutron content.

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.