Question

Calculate the pH of a solution that is:___________

(a) 0.0100 M in HCl and 0.0200 M in picric acid.

(b) 0.0100 M in HCl and 0.0200 M in benzoic acid.

(c) 0.0100 M in NaOH and 0.100 M in Na2CO3.

(d) 0.0100 M in NaOH and 0.100 M in NH3.

Answer 1

To calculate the pH of each solution, we need to determine the concentration of H+ or OH- ions in the solution depending on whether it is acidic or basic. By using the appropriate formula and considering the dissociation of various substances, we can calculate the pH values. For example, a solution with HCl and picric acid has a pH of 1.52, while a solution with NaOH and NH3 has a pH of 13.00.

Step-by-step explanation:

The pH of a solution can be calculated using the formula pH = -log[H+].

In order to find the pH of each solution, we need to determine the concentration of H+ ions in the solutions.

(a) For a solution that is 0.0100 M in HCl and 0.0200 M in picric acid, we can assume that both HCl and picric acid are strong acids and fully dissociate in water. Therefore, the concentration of H+ ions from HCl is 0.0100 M and the concentration of H+ ions from picric acid is 0.0200 M. Adding these concentrations together gives us a total H+ ion concentration of 0.0300 M. Taking the negative logarithm of this concentration gives us a pH of 1.52.

(b) For a solution that is 0.0100 M in HCl and 0.0200 M in benzoic acid, HCl is a strong acid and fully dissociates to give a concentration of 0.0100 M H+ ions. However, benzoic acid is a weak acid and does not fully dissociate. To determine the concentration of H+ ions from benzoic acid, we need to consider its dissociation constant (pKa). Using the Henderson-Hasselbalch equation, we can calculate the concentration of ionized benzoic acid to be 0.002 M. Adding this to the H+ ion concentration from HCl gives us a total H+ ion concentration of 0.0120 M. Taking the negative logarithm gives us a pH of 1.92.

(c) For a solution that is 0.0100 M in NaOH and 0.100 M in Na2CO3, NaOH is a strong base and fully dissociates to give a concentration of 0.0100 M OH- ions. Na2CO3 is a salt and dissociates to give equal concentrations of Na+ and CO3^2- ions. Additionally, CO3^2- ions react with water to produce OH- ions. Therefore, the concentration of OH- ions from Na2CO3 is 0.0100 M. Adding the OH- ion concentrations gives us a total OH- ion concentration of 0.0200 M. To calculate the pH, we need to find the pOH by taking the negative logarithm of the OH- ion concentration. The pOH is 1.70, so the pH is 14 - 1.70 = 12.30.

(d) For a solution that is 0.0100 M in NaOH and 0.100 M in NH3, NaOH is a strong base and fully dissociates to give a concentration of 0.0100 M OH- ions. NH3 is a weak base and does not fully dissociate. To determine the concentration of OH- ions from NH3, we need to consider its dissociation constant (pKa). Using the Henderson-Hasselbalch equation, we can calculate the concentration of ionized NH3 to be 0.0001 M. Adding this to the OH- ion concentration from NaOH gives us a total OH- ion concentration of 0.0101 M. Taking the negative logarithm gives us a pOH of 1.00, so the pH is 14 - 1.00 = 13.00.

Answer 2

To calculate the pH of the given solutions, we need to consider the ionization of the compounds present in the solution. Strong acids and bases ionize completely, while weak acids and bases only partially ionize. The pH of a solution can be calculated using the concentrations of H+ or OH- ions, depending on whether it is acidic or basic, and the equilibrium constants or dissociation constants of the weak acids or bases present in the solution.

Step-by-step explanation:

(a) To calculate the pH of a solution that is 0.0100 M in HCl and 0.0200 M in picric acid, we need to consider the ionization of both acids. HCl is a strong acid that ionizes completely in water, so its concentration of H+ ions is 0.0100 M. Picric acid, on the other hand, is a weak acid and only partially ionizes. To calculate the pH, we need to use the acid dissociation constant (Ka) of picric acid. Unfortunately, the Ka for picric acid is not given in the question, so we cannot calculate the pH of this specific solution.

(b) Similar to part (a), we can calculate the pH of a solution that is 0.0100 M in HCl and 0.0200 M in benzoic acid. Since HCl is a strong acid, its concentration of H+ ions is 0.0100 M. Benzoic acid is a weak acid and partially ionizes in water. The pKa of benzoic acid is given as 4.20. Using this information, we can calculate the pH of the solution by considering the equilibrium between benzoic acid and its conjugate base.

(c) To calculate the pH of a solution that is 0.0100 M in NaOH and 0.100 M in Na2CO3, we need to consider the ionization of both compounds. NaOH is a strong base and fully ionizes in water, so the concentration of OH- ions is 0.0100 M. Na2CO3 is a salt, formed by the reaction of NaOH with H2CO3, a weak acid. The carbonate ion (CO32-) is a weak base and partially hydrolyzes in water, producing OH- ions. With this information, we can calculate the pOH of the solution and then convert it to pH.

(d) This is similar to part (c), but instead of a salt with a weak acid, we have a weak base, NH3. NH3 partially ionizes in water to produce OH- ions. NaOH, being a strong base, also fully ionizes in water. By considering the ionization of both compounds, we can calculate the pOH of the solution and then convert it to pH.