A certain weak acid has a dissociation constant of 1.0 × 10 - 4 . The equilibrium constant for its reaction with a strong base is

Question

A certain weak acid has a dissociation constant of 1.0 × 10 - 4 . The equilibrium constant for its reaction with a strong base is (A)  1.0 × 10 - 4  (B)  1.0 × 10 - 10  (C)  1.0 × 10 10  (D)  1.0 × 10 14

Tardigrade Admin · Accepted Answer

The reaction of HA with strong base is HA + OH- leftharpoons H2O + A- K = ( [ A- ]/ [ HA ] [ OH-] ) × ( [ H+ ]/ [ H+ ] ) = ( Ka / Kw ) = ( 10 - 4 / 10 - 14 ) = 10 10

Q. A certain weak acid has a dissociation constant of $1.0 \times 1 0^{- 4}$ . The equilibrium constant for its reaction with a strong base is

$1.0 \times 1 0^{- 4}$

$1.0 \times 1 0^{- 10}$

$1.0 \times 1 0^{10}$

$1.0 \times 1 0^{14}$

The reaction of HA with strong base is
$H A + O H^{-} ⇌ H_{2} O + A^{-}$
K = $\frac{[ A ^{-} ]}{[ H A ] [ O H ^{-} ]} \times \frac{[ H ^{+} ]}{[ H ^{+} ]} = \frac{K _{a}}{K _{w}}$
= $\frac{1 0 ^{- 4}}{1 0 ^{- 14}} = 1 0^{10}$

Q. A certain weak acid has a dissociation constant of 1.0×10−4. The equilibrium constant for its reaction with a strong base is

1.0×10−4

1.0×10−10

1.0×1010

1.0×1014