Ch.15 - Acid and Base EquilibriumWorksheetSee all chapters
All Chapters
Ch.1 - Intro to General Chemistry
Ch.2 - Atoms & Elements
Ch.3 - Chemical Reactions
BONUS: Lab Techniques and Procedures
BONUS: Mathematical Operations and Functions
Ch.4 - Chemical Quantities & Aqueous Reactions
Ch.5 - Gases
Ch.6 - Thermochemistry
Ch.7 - Quantum Mechanics
Ch.8 - Periodic Properties of the Elements
Ch.9 - Bonding & Molecular Structure
Ch.10 - Molecular Shapes & Valence Bond Theory
Ch.11 - Liquids, Solids & Intermolecular Forces
Ch.12 - Solutions
Ch.13 - Chemical Kinetics
Ch.14 - Chemical Equilibrium
Ch.15 - Acid and Base Equilibrium
Ch.16 - Aqueous Equilibrium
Ch. 17 - Chemical Thermodynamics
Ch.18 - Electrochemistry
Ch.19 - Nuclear Chemistry
Ch.20 - Organic Chemistry
Ch.22 - Chemistry of the Nonmetals
Ch.23 - Transition Metals and Coordination Compounds
Sections
Identifying Acids and Bases
Arrhenius Acid and Base
Bronsted Lowry Acid and Base
Amphoteric
Lewis Acid and Base
pH and pOH
Ka and Kb
Ionic Salts
Diprotic Acid
Polyprotic Acid
Additional Practice
Conjugate Acids and Bases
Strong Acid-Base Calculations
Weak Acids
Weak Bases
Additional Guides
Strong Acids and Strong Bases
LearnAdditional PracticeSummary
Next SectionPolyprotic Acid

A diprotic acid is an acid that can donate two hydronium ions (H+). 

Diprotic Acids

Since a diprotic acid has two acidic hydrogens it would have 2 equilibrium equations. 

Concept #1: Diprotic Acids

The diprotic bases would also have 2 equilibrium equations. 

Concept #2: Diprotic Acids

Concept #3: As a result of these equations for diprotic acids and bases the relationship between Ka and Kb can be established. 

Example #1: Sulfurous acid, H2SO3, represents a diprotic acid with a Ka1 = 1.6 x 10-2 and Ka2 = 4.6 x 10-5. Calculate the pH and concentrations of H2SO3, HSO3– and SO32– when given 0.250 M H2SO3. 

Example #2: Determine the pH of 0.115 M Na2S. Hydrosulfuric acid, H2S, contains Ka1 = 1.0 x 10-7 and Ka2 = 9.1 x 10-8.

Previous SectionIonic Salts
Next SectionPolyprotic Acid
Additional Problems
Identify the weak diprotic acid. A) CH3COOH B) HCOOH C) H3PO4 D) H2SO4 E) H2CO3
Calculate the concentration of H+ ions in a 0.010 M aqueous solution of sulfuric acid. Express your answer to three decimal places and include the appropriate units.
Write the chemical equation for the reaction of carbonic acid (H 2CO3) with water.
For the diprotic weak acid H2A, Ka1 = 3.1 X 10-6 and Ka2 = 5.1 X 10-9. What is the pH of a 0.0500 M solution of H2A? What are the equilibrium concentrations of H2A and A2- in this solution?pH = ?H2A = ?A2- = ?
Write chemical equations and corresponding equilibrium expressions for each of the two ionization steps of carbonic acid.Express as chemical equation; identify all phases.a. Write chemical equations for first ionization step of carbonic acid.b. Write chemical equations for second ionization step of carbonic acid.
Complete the Ka2 expression for H2CO3 in an aqueous solution. Ka2 = 4.69 x 10-11
Which one of the following is a diprotic acid?a. sulfuric acidb. nitric acidc. barium hydroxided. chloric acid
Identify the weak diprotic acid.A) CH3COOHB) HCOOHC) H3PO4D) H2SO4E) H2CO3
H2CO3 is a diprotic acid. The pKa for H2CO3 is 6.35 and the pKa for HCO3- = 10.33. At pH = 9.0, what is the approximate relative quantities of H2CO3, HCO3-, and CO32-? a. 1 H2CO3, 10 HCO3-, and 1 CO32- b. Negligible H2CO3, 95 HCO3-, and 5 CO32- c. 1 H2CO3, 90 HCO3-, and 10 CO32- d. Negligible H2CO3, 75 HCO3-, and 25 CO32-
Write the equation for the reaction associated with:The Ka2 of sulfuric acid (H2SO4).The Kb2 of carbonate in water (CO32-)Explain in your own words why you do not need a K-value to calculate the dissociation of a strong acid?
Calculate the pH of a 0.080 M carbonic acid solution, H 2CO3(aq), that has the stepwise dissociation constants Ka1 = 4.3 × 10 -7 and Ka2 = 5.6 × 10 -11.A) 1.10B) 3.73C) 6.37D) 10.25
Ascorbic acid, H2C6H6­O6, is a common diprotic acid with a Ka1 = 8.0 x 10 -5 and Ka2 = 1.6 x 10 -12.a. What are the three forms of the diprotic acid?   b. What is the principal species at pH = 2.00?  c. What is the principal species at pH = 6.10?  d. What is the principal species at 13.80?  e. What is the second most prominent species at pH = 8.10?  f. At what pH is [H2C6H6­O6] = [HC6H6­O6 - ]?  g. At what pH is [HC6H6­O6 - ] = [C6H6­O62 - ]? 
What is the difference between (a) a monoprotic acid and a diprotic acid?
The pKa's for carbonic acid and bicarbonate at 37°C are 3.83 and 10.25, respectively. Write the equation for each of these equilibria.
Explain the following observations: (c) although sulfuric acid is a strong electrolyte, an aqueous solution of H2SO4 contains more HSO4– ions than SO42– ions.
Calculate the equilibrium concentration of C2O42− in a 0.20 M solution of oxalic acid.Express your answer to two significant figures and include the appropriate units.
Enter your answer in the provided box.A 4.00-g quantity of a diprotic acid was dissolved in water and made up to exactly 3.00 x 102 mL. Calculate the molar mass of the acid if 25.0 mL of this solution required 11.6 mL of 1.00 M KOH for neutralization. Assume that both protons of the acid were titrated.
Complete the Ka2 expression for H2CO3 in an aqueous solution. 
What is the pH of a 0.310 M solution of H2SO4? Ka2 = 1.20 x 10^-2