Concept explainers
Calculate the pH at
Interpretation:
The pH of the solution that contains phosphoric acid with given concentration is to be determined.
Concept introduction:
The first ionization of the polyprotic acid takes place as
The second ionization of the polyprotic acid takes place as
The third ionization of the polyprotic acid takes place as
Percent ionization is the percentage of acid that gets dissociated upon addition to water. It depends on the hydronium ion concentration.
Here,
pH of the solution is calculated as
Answer to Problem 88QP
Solution:
The pH of the solution is
Explanation of Solution
Given information:
The concentration of phosphoric acid
When phosphoric acid is dissolved in water, the dissociation takes place in three steps as it is a triprotic acid. First, one proton is partially dissociated because phosphoric acid is a weak acid. Thus, the pH of the solution is determined by the contribution made by all the three proton dissociation steps.
The reaction of the first proton dissociation of phosphoric acid is depicted as
Prepare an equilibrium table and represent each of the species in terms of
Now, substitute these concentrations in equation (1) as
Because the value of
Thus,
Calculate the percent dissociation from equation (4) as
Since the percent dissociation is more than
Since concentration cannot be negative, so
Thus,
Now, the reaction of the second proton dissociation of phosphoric acid is depicted as
Prepare an equilibrium table and represent each of the species in terms of
Now, substitute these concentrations in equation (2) as
Since the value of
Thus,
Calculate the percent dissociation from equation (4) as
Since the percent dissociation is much less than
Now, the reaction of the third proton dissociation of phosphoric acid is depicted as
Prepare an equilibrium table and represent each of the species in terms of
Now, substitute these concentrations in equation (3):
Since the value of
Thus,
Calculate the percent dissociation from equation (4) as
Since the percent dissociation is much less than
Also,
Substitute this value in equation (5) to calculate pH of the solution:
The pH of the phosphoric acid solution is
Want to see more full solutions like this?
Chapter 16 Solutions
Connect 1-semester Access Card For Chemistry
- A solution of baking soda, NaHCO3, has a pH of 10.08. What is the percent (by mass) of NaHCO3 in a 235-mL solution? (Assume a density of 1.00 g/mL.)arrow_forwardClassify each of the following substances as an acid, a base, or a salt. a. AlPO4 b. KOH c. HNO3 d. HC2H3O2arrow_forwardThe pH of a 0.10-M solution of propanoic acid, CH3CH2COOH, a weak organic acid, is measured at equilibrium and found to be 2.93 at 25 °C. Calculate the Ka of propanoic acid.arrow_forward
- What is the pH of a solution obtained by mixing 235 mL of NaOH with a pH of 11.57 and 316 mL of Sr(OH)2 with a pH of 12.09? Assume that volumes are additive.arrow_forwardWrite the reaction and the corresponding Kb equilibrium expression for each of the following substances acting as bases in water. a. aniline, C6H5NH2 b. dimethylamine, (CH3)2NHarrow_forwardWhat is the pH of a 0.020 M solution of H2SO4? You may assume that the first ionization is complete. The second ionization constant is 0.010.arrow_forward
- Chemistry: Principles and PracticeChemistryISBN:9780534420123Author:Daniel L. Reger, Scott R. Goode, David W. Ball, Edward MercerPublisher:Cengage LearningChemistry: The Molecular ScienceChemistryISBN:9781285199047Author:John W. Moore, Conrad L. StanitskiPublisher:Cengage LearningIntroductory Chemistry: A FoundationChemistryISBN:9781285199030Author:Steven S. Zumdahl, Donald J. DeCostePublisher:Cengage Learning
- Chemistry: Principles and ReactionsChemistryISBN:9781305079373Author:William L. Masterton, Cecile N. HurleyPublisher:Cengage LearningGeneral, Organic, and Biological ChemistryChemistryISBN:9781285853918Author:H. Stephen StokerPublisher:Cengage LearningChemistry: An Atoms First ApproachChemistryISBN:9781305079243Author:Steven S. Zumdahl, Susan A. ZumdahlPublisher:Cengage Learning