Correct Answer: B

Rationale: The correct answer is B, Dalton's law. Dalton's law states that in a mixture of non-reacting gases, the total pressure is equal to the sum of the partial pressures of the individual gases. The equation Ptot = Pa + Pb represents Dalton's law, where Ptot is the total pressure, and Pa and Pb are the component pressures. Choice A, Henry's law, deals with the solubility of gases in liquids. Choice C, Boyle's law, describes the inverse relationship between the pressure and volume of a gas at constant temperature. Choice D, Gay-Lussac's law, states that the pressure of a gas is directly proportional to its absolute temperature when volume is constant.

Correct Answer: B

Rationale: Oxygen typically has an oxidation number of -2 in compounds because it tends to gain electrons. This is due to its high electronegativity, which leads to oxygen attracting electrons towards itself in a chemical bond. Choice A (2) is incorrect because oxygen doesn't have a +2 oxidation number in compounds. Choice C (0) is incorrect as oxygen rarely has an oxidation number of 0 in compounds. Choice D (-1) is incorrect as oxygen's oxidation number in compounds is typically -2, not -1.

Correct Answer: A

Rationale: Brownian motion is the correct choice as it specifically refers to the spontaneous, random movement of small particles suspended in a liquid, caused by the unbalanced impacts of molecules on the particle. This phenomenon was observed and documented by Robert Brown, leading to the discovery of the existence of molecules. Grey's kinesis and Boyle's wave are not scientifically recognized terms related to this concept.

Correct Answer: C

Rationale: The English scientist who made accurate observations on how pressure and volume are related was Robert Boyle. Boyle's law states that the pressure of a gas is inversely proportional to its volume when the temperature is constant. This fundamental gas law was discovered by Robert Boyle in the 17th century and laid the groundwork for our understanding of the behavior of gases. Choices A, B, and D are incorrect. Charles refers to Charles's law, not Boyle. Combine is not related to the topic, and Gay-Lussac is associated with Gay-Lussac's law, not Boyle's law.

Correct Answer: A

Rationale: Statement A is correct. pH is a measure of the effective concentration of hydrogen ions in a solution, and it is related to the molarity of H+ by the formula pH = - log [H+]. This equation illustrates the logarithmic relationship between pH and the concentration of hydrogen ions. Oxygen ions and hydrogen atoms are not directly related to pH in the same manner as hydrogen ions. Acidity is determined by the concentration of hydrogen ions in a solution, and this concentration is what pH measures. Therefore, option A is the only statement that correctly defines the relationship between pH and the concentration of hydrogen ions in a solution. Choices B, C, and D are incorrect as they provide inaccurate information about the relationship between pH and the ions/atoms mentioned. Option B incorrectly associates pH with oxygen ions, option C mentions hydrogen atoms instead of hydrogen ions, and option D confuses acidity with pH, which is a measure of hydrogen ion concentration, not molarity.