Which of these aqueous solutions has the lowest pH A) 0.100 M NaOH B) 0.100 M Na₂O C) 0.100 M Na₃N D) All of these solutions have the same pH due to the leveling effect. E) These all are solutions of weak bases, so K_b values are needed in order to decide.

Question

Quizplus · Accepted Answer

NaOH is a strong base and completely dissociates in water, producing hydroxide ions (OH-) which increase the concentration of OH- ions and decrease the pH of the solution. Na₂O and Na₃N are salts of weak acids (HSO4- and H2PO4-) and weak bases (HS- and HPO42-) respectively, and undergo hydrolysis in water, leading to a basic solution. However, since the concentrations are the same for all solutions, the difference in pH caused by the hydrolysis is not enough to overcome the strong acidity of NaOH, resulting in the lowest pH for solution A. Choice D is incorrect because the solutions are not equivalent due to their different chemical properties. Choice E is incorrect because NaOH is a strong base and does not require a Ka or Kb value to determine its acidity/basicity.

Which of These Aqueous Solutions Has the Lowest PH