Ch.15 - Acid and Base EquilibriumWorksheetSee all chapters
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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
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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

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.

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.
Calculate the concentration of all species in a 0.160 M solution of H2 CO3.Calculate the concentration of H2CO3.
Calculate the concentration of all species in a 0.160 M solution of H2 CO3.Calculate the concentration of CO32-.
Calculate the concentration of all species in a 0.160 M solution of H2 CO3.Calculate the concentration of H3O+.
Consider a 0.10 M solution of a weak polyprotic acid (H2 A) with the possible values of Ka1 and Ka2 given below. Calculate the contributions to [H3O+] from each ionization step.Ka1 = 1.0 10 - 4 ; Ka2 = 5.0 10 - 5
Consider a 0.10 M solution of a weak polyprotic acid (H2 A) with the possible values of Ka1 and Ka2 given below. Calculate the contributions to [H3O+] from each ionization step.Ka1 = 1.0 10 - 4 ; Ka2 = 1.0 10 - 5
Consider a 0.10 M solution of a weak polyprotic acid (H2 A) with the possible values of Ka1 and Ka2 given below. Calculate the contributions to [H3O+] from each ionization step.Ka1 = 1.0 10 - 4 ; Ka2 = 1.0 10 - 6
State whether each of the following statements is true or false. Justify your answer in each case.Sulfuric acid is a monoprotic acid.
When calculating the [H3O+] for a polyprotic acid, the second ionization step can often be neglected.Explain why this is so.
For a weak diprotic acid H2X, what is the relationship between [X2-] and Ka2? Under what conditions does this relationship exist?
Determine the pH of each of the following two-component solutions.8.0×10−2 M RbOH and 0.120 M NaHCO3
Classify each of the following acids as strong or weak.Write an expression for the acid ionization constant (Ka ) for H2 CO3.
A mixture of NaCN and NaHSO4 consists of a total of 0.60 mol. When the mixture is dissolved in 1.0 L of water and comes to equilibrium the pH is found to be 9.6.Find the amount of NaCN in the mixture.
The following observations are made about a diprotic acid H2A: (i) A 0.10 M solution of H2A has pH=3.30. (ii) A 0.10 M solution of the salt NaHA is acidic.Which of the following could be the value of pKa2 for H2A:
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.
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-
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.
Calculate the concentration of all species in a 0.510 M solution of H2 SO3. The acid ionization constants for the acid are Ka1 = 1.6 x 10-2 and Ka2 = 6.4 x 10-8.
The pH of human blood is steady at a value of approximately 7.4 owing to the following equilibrium reactions:CO2(aq) + H2O(l) ⇌ H2CO3(aq) ⇌ HCO3-(aq) + H+(aq)Acids formed during normal cellular respiration react with the HCO 3- to form carbonic acid, which is in equilibrium with CO2(aq) and H2O(l). During vigorous exercise, a person’s H 2CO3 blood levels were 26.3 mM, whereas his CO2 levels were 1.63 mM. On resting, the H 2CO3 levels declined to 24.9 mM. What was the CO2 blood level at rest?
Tartaric acid is found in many fruits, including grapes, and is partially responsible for the dry texture of certain wines. The acid-dissociation constants for tartaric acid are Ka1 = 1.0x10-3 and Ka2 = 4.6x10-5. Calculate the pH for a 0.305 M{ m ;{ m M}} solution of tartaric acid.
Tartaric acid is found in many fruits, including grapes, and is partially responsible for the dry texture of certain wines. The acid-dissociation constants for tartaric acid are Ka1 = 1.0x10-3 and Ka2 = 4.6x10-5. Did you have to make any approximations or assumptions in your calculation?
Tartaric acid is found in many fruits, including grapes, and is partially responsible for the dry texture of certain wines. The acid-dissociation constants for tartaric acid are Ka1 = 1.0x10-3 and Ka2 = 4.6x10-5. Calculate the tartarate ion (C4H4O62–) concentration for a 0.305 M { m ;{ m M}} solution of tartaric acid.
Is an aqueous solution of NaHSO 4 acidic, basic, or neutral? What reaction occurs with water? Calculate the pH of a 0.10-M solution of NaHSO4.
Using the table below, how many of the following salts are expected to produce acidic solutions: NaHSO4, NaHC2O4, NaH2PO4, and NaHCO3?
Succinic acid (H2C4H6O4), which we will denote H2Suc, is a biologically relevant diprotic acid with the structure shown below.It is closely related to tartaric acid and malic acid. At 25 o C, the acid-dissociation constants for succinic acid are Ka1 = 6.9 x 10-5 and Ka2 = 2.5  x 10-6. Determine the pH of a 0.31 M solution of H2Suc at 25 oC, assuming that only the first dissociation is relevant.
Succinic acid (H2C4H6O4), which we will denote H2Suc, is a biologically relevant diprotic acid with the structure shown below.It is closely related to tartaric acid and malic acid. At 25 o C, the acid-dissociation constants for succinic acid are Ka1 = 6.9 x 10-5 and Ka2 = 2.5  x 10-6. Will a solution of the salt NaHSuc be acidic, neutral, or basic?
Oxalic acid (H2C2O4) is a diprotic acid. Using the acid-dissociation constants for oxalic acid (Ka1=5.9 x 10-2, Ka2=6.4 x 10-5), determine whether each of the following statements is true.H2C2O4 can serve as both a Brønsted-Lowry acid and a Brønsted-Lowry.
Oxalic acid (H2C2O4) is a diprotic acid. Using the acid-dissociation constants for oxalic acid (Ka1=5.9 x 10-2, Ka2=6.4 x 10-5), determine whether each of the following statements is true.An aqueous solution of the strong electrolyte KHC2O4 will have pH < 7.
Use Appendix C to calculate [H 2S], [HS−], [S2−], [H3O+], pH, [OH−], and pOH in a 0.10 M solution of the diprotic acid hydrosulfuric acid.
Atmospheric CO2 levels have risen by nearly 20% over the past 40 years from 315 ppm to 380 ppm.Given that the average pH of clean, unpolluted rain today is 5.4, determine the pH of unpolluted rain 40 years ago. Assume that carbonic acid (H2CO3) formed by the reaction of CO2 and water is the only factor influencing pH.CO2(g) + H2O(l) ⇌ H2CO3(aq)
Use Appendix C to calculate [H 2C3H2O4], [HC3H2O4−], [C3H2O42−] , [H3O+], pH, [OH−], and pOH in a 0.200 M solution of the diprotic acid malonic acid.
What is the concentration of X2- in a 0.150 M solution of the diprotic acid H2X? For H2X, Ka1  = 4.5 x 10 - 6 and Ka2  = 1.2 x 10 - 11.
Write out the stepwise Ka reactions for the diprotic acid H2SO3.
A typical vitamin C tablet (containing pure ascorbic acid, H2C6H6O6) weighs 500. mg. One vitamin C tablet is dissolved in enough water to make 200.0 mL of solution. Calculate the pH of this solution. Ascorbic acid is a diprotic acid.
Calculate the pH and [S 2-] in a 0.10-M H 2S solution. Assume Ka1 = 1.0 X 10 -7; Ka2 = 1.0 X 10-19.
Calculate [CO32-] in a 0.010-M solution of CO 2 in water (usually written as H 2CO3). If all the CO32- in this solution comes from the reactionHCO3-(aq) ⇌ H+(aq) + CO32-(aq)what percentage of the H+ ions in the solution is a result of the dissociation of HCO 3-? When acid is added to a solution of sodium hydrogen carbonate (NaHCO3), vigorous bubbling occurs. How is this reaction related to the existence of carbonic acid (H2CO3) molecules in aqueous solution?
Calculate the pH of a 2.0-M H 2SO4 solution.
Calculate the pH of a 5.0 X 10 -3-M solution of H 2SO4.
When carbon dioxide dissolves in water, it undergoes a multistep equilibrium process, with Koverall = 4.5 x 10−7, which is simplified to the following: CO2(g) + H2O(l) ⇌ H2CO3(aq) H2CO3(aq) + H2O(l) ⇌ HCO3−(aq) + H3O+(aq)(b) What is the pH of nonpolluted rainwater in equilibrium with clean air (PCO 2 in clean air = 4 x 10−4 atm; Henry’s law constant for CO 2 at 25°C is 0.033 mol/L•atm)?
When carbon dioxide dissolves in water, it undergoes a multistep equilibrium process, with Koverall = 4.5 x 10−7, which is simplified to the following: CO2(g) + H2O(l) ⇌ H2CO3(aq) H2CO3(aq) + H2O(l) ⇌ HCO3−(aq) + H3O+(aq)(c) What is [CO32−] in rainwater (Ka of HCO3− = 4.7 x 10−11)?
Which of the following concentrations would be practically equal in a calculation of the equilibrium concentrations in a 0.134-M solution of H2CO3, a diprotic acid: [H3 O+], [OH−], [H2CO3], [HCO3 −], [CO3 2−]? No calculations are needed to answer this question.
Calculate the concentration of each species present in a 0.050-M solution of H2S.
Calculate the concentration of each species present in a 0.010-M solution of phthalic acid, C6H4(CO2H)2.C6 H4(CO2 H)2(aq) + H2 O(l) ⇌ H3 O+(aq) + C6 H4 (CO2 H) (CO2 )−(aq)        K a = 1.1 × 10−3C6 H4(CO2 H)(CO2)(aq) + H2 O(l) ⇌ H3 O+(aq) + C6 H4(CO2)2 2−(aq)            K a = 3.9 × 10−6
Salicylic acid, HOC6H4CO2H, and its derivative have been used as pain reliever for a long time. Salicylic acid occurs in small amount in the leaves, bark, and roots of some vegetation (most notably historically in the bark of the willow tree). Extracts of this plant have been used as medication for century. The acid was first isolated in the laboratory in 1838.(a) Both functional groups of salicylic acid ionize in water, with K a = 1.0 × 10−3 for the—CO2H group and 4.2 × 10−13 for the −OH group. What is the pH of a saturated solution of the acid (solubility = 1.8 g/L).
Salicylic acid, HOC6H4CO2H, and its derivative have been used as pain reliever for a long time. Salicylic acid occurs in small amount in the leaves, bark, and roots of some vegetation (most notably historically in the bark of the willow tree). Extracts of this plant have been used as medication for century. The acid was first isolated in the laboratory in 1838.(a) Both functional groups of salicylic acid ionize in water, with Ka = 1.0 × 10−3 for the—CO2H group and 4.2× 10−13 for the −OH group. What is the pH of a saturated solution of the acid (solubility = 1.8 g/L).(b) Aspirin was discovered as a result of efforts to produce a derivative of salicylic acid that would not be irritating to the stomach lining. Aspirin is acetylsalicylic acid, CH3CO2C6H4CO2H. The −CO2H functional group is still present, but its acidity is reduced, K a = 3.0 × 10−4. What is the pH of a solution of aspirin with the same concentration as a saturated solution of salicylic acid (See Part a).
Salicylic acid, HOC6H4CO2H, and its derivative have been used as pain reliever for a long time. Salicylic acid occurs in small amount in the leaves, bark, and roots of some vegetation (most notably historically in the bark of the willow tree). Extracts of this plant have been used as medication for century. The acid was first isolated in the laboratory in 1838.(c) Under some conditions, aspirin reacts with water and forms a solution of salicylic acid and acetic acid: CH3 CO2 C6 H4 CO2 H(aq) + H2 O(l) ⟶ HOC6 H4 CO2 H(aq) + CH3 CO2 H(aq)i. Which of the acids, salicylic acid or acetic acid, produces more hydronium ions in such a solution?ii. What are the concentrations of molecules and ions in a solution produced by the hydrolysis of 0.50 g of aspirin dissolved in enough water to give 75 mL of solution?
The ion HTe− is an amphiprotic specie; it can act as either an acid or a base.(c) Demonstrate whether or not the second ionization of H 2Te can be neglected in the calculation of [HTe−] in a 0.10 M solution of H 2Te.
Find the pH of a solution that is 8.0×10−2 M in H2CO3.
Find the pH of a 0.0065 M sulfuric acid solution.
Find [SO42-] of a 0.0065 M sulfuric acid solution.
Write chemical equations for first ionization step of carbonic acid.
Write corresponding equilibrium expressions for first ionization step of carbonic acid.
Write chemical equations for second ionization step of carbonic acid.
Write corresponding equilibrium expressions for second ionization step of carbonic acid.
What is the pH of 1.000 L of a solution of 100.0 g of glutamic acid (C  5H9NO4, a diprotic acid; K1 = 8.5 × 10−5, K2 = 3.39 × 10−10) to which has been added 20.0 g of NaOH during the preparation of monosodium glutamate, the flavoring agent? What is the pH when exactly 1 mol of NaOH per mole of acid has been added?
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
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?
Complete the Ka2 expression for H2CO3 in an aqueous solution.Ka2 = 4.69 x 10-11
Complete the Ka2 expression for H2CO3 in an aqueous solution. Ka2 = 4.69 x 10-11