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
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: