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
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Ch.11 - Liquids, Solids & Intermolecular Forces
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Ch.14 - Chemical Equilibrium
Ch.15 - Acid and Base Equilibrium
Ch.16 - Aqueous Equilibrium
Ch. 17 - Chemical Thermodynamics
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Ch.19 - Nuclear Chemistry
Ch.20 - Organic Chemistry
Ch.22 - Chemistry of the Nonmetals
Ch.23 - Transition Metals and Coordination Compounds

Solution: Given the following Kb values, rank the conjugate acids of these bases in order of increasing acid strength.HS–                Kb = 1.0 × 10–7HCOO–          Kb = 5.6 × 10–11CH3NH2         Kb = 4.4 × 1

Problem

Given the following Kb values, rank the conjugate acids of these bases in order of increasing acid strength.
HS                Kb = 1.0 × 10–7

HCOO          Kb = 5.6 × 10–11

CH3NH2         Kb = 4.4 × 10–4

SO3–2             Kb = 1.6 × 10–7

BrO               Kb = 4.0 × 10–6 

A. CH3NH3+ < H2S < HCOOH < HSO3 < HBrO

B. CH3NH3+ < HBrO < HSO3 < H2S < HCOOH

C. H2S < HSO3 < HCOOH < CH3NH3< HBrO

D. HCOOH < H2S < HSO3 < HBrO < CH3NH3+

E. H2S < HCOOH < HSO3 < CH3NH3+ < HBrO


Solution

We’re being asked to rank the conjugate acids of these bases in order of increasing acid strength given their following Kb values,


Ka represents the acid dissociation constant and it measures the strength of weak acids.

• The higher the Ka the stronger the acid and the greater the concentration of H+
• The lower the Ka, the weaker the acid and the lesser the concentration of H+


The Ka of a conjugate acid can be calculated from the Kb of a base.  Ka and Kb are connected by the autoionization constant of water (Kw) in the following equation:

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