A diprotic acid is an acid that can donate two hydronium ions (H+).
Since a diprotic acid has two acidic hydrogens it would have 2 equilibrium equations.
Concept: Diprotic Acids4m
The diprotic bases would also have 2 equilibrium equations.
Concept: Diprotic Acids3m
Concept: As a result of these equations for diprotic acids and bases the relationship between Ka and Kb can be established.5m
Example: 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 H2SO3.14m
Example: Determine the pH of 0.115 M Na2S. Hydrosulfuric acid, H2S, contains Ka1 = 1.0 x 10-7 and Ka2 = 9.1 x 10-8.7m
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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
Complete the Ka2 expression for H2CO3 in an aqueous solution. Ka2 = 4.69 x 10-11
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.
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 the chemical equation for the reaction of carbonic acid (H 2CO3) with water.
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.
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.
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 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.
Identify the weak diprotic acid.
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 - ]?
Identify the weak diprotic 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.