Question

what is the ph of a solution made by mixing 0.30 molnaoh , 0.25 molna2hpo4 , and 0.20 molh3po4 with water and diluting to 1.00 l ? express your answer using two decimal places.

Answer 1

To calculate the pH of the solution, we need to calculate the concentrations of H+ ions in the solution. From the concentrations given for [H₂PO4¯], [HPO42-], and [OH-], we can determine the concentration of H+ ions using the equilibrium constant expression for the dissociation of phosphoric acid. Then, we can calculate the pOH and pH of the solution using the relationship pH + pOH = 14.

Step-by-step explanation:

To determine the pH of the solution, we need to consider the dissociation of the acids and bases present.

The given solution consists of NaOH, Na2HPO4, and H3PO4. NaOH is a strong base, so it completely dissociates into Na+ and OH- ions. Na2HPO4 and H3PO4 are weak acids, so they partially dissociate into H+ and their respective conjugate base.

To calculate the pH of the solution, we need to calculate the concentrations of H+ ions in the solution. From the concentrations given for [H₂PO4¯], [HPO42-], and [OH-], we can determine the concentration of H+ ions using the equilibrium constant expression for the dissociation of phosphoric acid. Then, we can calculate the pOH and pH of the solution using the relationship pH + pOH = 14.

Answer 2

The pH of the solution is approximately 0.47.

Step-by-step explanation:

The pH of a solution can be calculated using the equation:

pH = -log[H+]

First, we need to determine the concentration of H+ ions in the solution. From the given information, we can see that the concentration of H₂PO4¯ is 0.042 M and the concentration of HPO42- is 0.341 M. Since H₂PO4¯ and HPO42- are in equilibrium with H+, we can assume that they have the same concentration. Thus, the concentration of H+ is 0.342 M.

Taking the negative logarithm (base 10) of 0.342 M, we get:

pH = -log(0.342) = 0.467

Therefore, the pH of the solution is approximately 0.47.