Question

WHAT IS THE HYDROGEN ION CONCENTRATION OF 0.1N BORIC ACID

A)1.5X10^-12
B)3.7X10^-8
C)4.82X10^-4
D)6.3X10^-6

Answer 1

Answer on Question #70767 – Chemistry – Other

Task:

What is the hydrogen ion concentration of 0.1 N boric acid.

A) $1.15 \times 10^{-12}$;

B) $3.7 \times 10^{-8}$;

C) $4.82 \times 10^{-4}$;

D) $6.3 \times 10^{-6}$.

Solution:

The dissociation of boric acid in the first stage proceeds according to the reaction:

$$H_3BO_3^- = H^+ + H_2BO_3^-,$$

For which the dissociation constant $K_{d1} = 5.8 \times 10^{-10}$,

$$K_{d1} = \frac{[H_2BO_3^-] \cdot [H^+]}{[H_3BO_3^-]} = 5.8 \times 10^{-10}.$$

The second and third stages of dissociation of boric acid are neglected.

$$[H^+] = \sqrt{K_{d1} \cdot C_m} = 6.3 \times 10^{-6}.$$

Answer: D) $6.3 \times 10^{-6}$ mol/dm³.

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