HESI A2 Chemistry Practice Test

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).

Correct Answer: A

Rationale: Correct Answer: A Rationale: 1. pH is a measure of hydrogen ion concentration in a solution. 2. The formula for pH is pH = - log[H+]. 3. This formula indicates an inverse logarithmic relationship between pH and H+ concentration. 4. The effective concentration of hydrogen ions directly influences pH. 5. The molarity of H+ ions is crucial in determining the pH value of a solution. Summary: Choice A is correct as it accurately describes the relationship between pH and hydrogen ion concentration, supported by the logarithmic formula. Choices B, C, and D are incorrect as they misinterpret the role of pH and its relationship to hydrogen ions in a solution.

Correct Answer: A

Rationale: The correct answer is A because at high pressure and high temperature, real gases have increased kinetic energy and are closer together, leading to decreased intermolecular forces. This results in gas molecules behaving more like ideal gases with negligible volume and no intermolecular interactions. Choice B is incorrect because at low pressure, real gases have low kinetic energy and are far apart, causing intermolecular forces to become more significant, deviating from ideal behavior. Choice C is incorrect as the boiling point of water is a specific condition related to water and does not necessarily indicate ideal gas behavior. Choice D is incorrect because under certain conditions of high pressure and high temperature, real gases can approach ideal behavior, demonstrating that real gases can exhibit ideal behavior under specific circumstances.

Correct Answer: A

Rationale: The correct answer is A: Covalent bonds. Covalent bonds involve a complete sharing of electrons between atoms with partially filled outer shells. This sharing allows atoms to achieve stable electron configurations. Hydrogen bonds involve an electrostatic attraction between a hydrogen atom and a highly electronegative atom. Proportional bonds are not a recognized type of chemical bond. Choice D, N/A, is not a valid option for this question.

Correct Answer: D

Rationale: Rationale: 1. Statement A is correct as solubility is indeed defined by the concentration in a saturated solution. 2. Statement B is correct as substances with very low solubilities are typically considered insoluble. 3. Statement C is correct as a saturated solution cannot dissolve any more solute. 4. Therefore, all statements (A, B, and C) are correct, making option D the correct choice. Other options are incorrect as they do not accurately define solubility or saturated solutions.