8. Monoprotic Acid-Base Equilibria
Weak Acid-Base Equilibria
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The pH of an aqueous 0.10 M nitrite ion is 8.17. What is the base dissociation constant of the base?
A
4.6 x 10-16
B
2.2 x 10-11
C
1.6 x 10-6
D
1.6 x 10‑5
E
1.2 x 10-3
Verified step by step guidance1
Identify the chemical species involved: The nitrite ion (NO2-) acts as a base in water, accepting a proton to form HNO2.
Use the given pH to find the concentration of hydroxide ions (OH-): Since pH + pOH = 14, calculate pOH as 14 - 8.17.
Convert pOH to [OH-]: Use the formula [OH-] = 10^(-pOH) to find the concentration of hydroxide ions.
Write the base dissociation equation: NO2- + H2O ⇌ HNO2 + OH-. The equilibrium expression for the base dissociation constant (Kb) is Kb = [HNO2][OH-] / [NO2-].
Substitute known values into the Kb expression: Use the initial concentration of NO2- (0.10 M) and the calculated [OH-] to solve for Kb, assuming [HNO2] ≈ [OH-] at equilibrium.
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