Question

In: Chemistry

For an acid-conjugate base pair, when the pH is qual to the pKa, the following is...

For an acid-conjugate base pair, when the pH is qual to the pKa, the following is true;

a. The acid concentration is the same as that of the conjugate base.

b. The acid concentration is twice that of the conjugate base.

c. There is only one species present in solution.

d. A and C

e. None of the above

Solutions

Expert Solution

Ans. For a weak acid, the dissociation reaction can written as follow-

                        AH + H2O --------> A-(aq) + H+(aq)

Using Henderson- Hasselbalch equation-

            pH = pKa + log ([A-] / [AH])                    - equation 1

            where, [A-] = base

[AH] = weak acid

Assuming pH = pKa in equation 1-

            pH – pKa = log ([A-] / [AH])

            Or, 0 = log ([A-] / [AH])

            Or, [A-] / [AH] = antilog 0 = 1

            Hence, [A-] = [AH]

That is, at pH = pKa, the concertation of acid (AH) is equal to the concertation of its conjugate base (A-).

So,

Correct option is- A.

           


Related Solutions

Acetic acid and its conjugate base acetate can form an acid-base buffer. The pKa of acetic...
Acetic acid and its conjugate base acetate can form an acid-base buffer. The pKa of acetic acid is 4.75. How much 10.0 M HNO3 must be added to 1.00 L of a buffer that is 0.0100 M acetic acid and 0.100 M sodium acetate to reduce the pH to 4.85 ?
Identify the acid and conjugate base in each reaction. Calculate the pKA for each acid. List...
Identify the acid and conjugate base in each reaction. Calculate the pKA for each acid. List them in order from the strongest to weakest acid. HC2H3O2 + H2O --> H3O+ + C2H3O2-, KA = 1.7 x 10-5 HC7H5O2 + H2O --> H3O+ + C7H5O2-, KA = 6.3 x 10-5 HC6H4NO2+H2O --> H3O+ + C6H4NO2-, KA = 1.4 x 10-5
Which of the following is/are a conjugate acid-base pair? HCN and CN- HNO3 and NO3- HClO4...
Which of the following is/are a conjugate acid-base pair? HCN and CN- HNO3 and NO3- HClO4 and Cl- KOH and OH- HNO3 and HNO2
identify the correct acid and conjugate base pair in this equation: HNO2 + HS - -->...
identify the correct acid and conjugate base pair in this equation: HNO2 + HS - --> NO2- + H2S A. HNO2 is an acid and NO2- is the conjugate base. B. HNO2 is an acid and H2S is the conjugate base. C. HS- is an acid and NO2- is the conjugate base. D. HS- is an acid and H2S is the conjugate base. E. There is not an acid and conjugate base pair in the equation given.
The pH of a 0.392 M solution of the conjugate base, A-, of a weak acid,...
The pH of a 0.392 M solution of the conjugate base, A-, of a weak acid, HA, is 11.60. What is the Kb for A-? Please show work
Select the pair of substances in which an acid is listed followed by its conjugate base....
Select the pair of substances in which an acid is listed followed by its conjugate base. A) H+, HCl B) NH3, NH4+ C) HPO42-, H2PO4- D) HCO3-, CO32- E) CH3COOH, CH3COOH2+
What is the conjugate acid of each of the following? What is the conjugate base of...
What is the conjugate acid of each of the following? What is the conjugate base of each? a) C4H8NH b) H2C6H5O7− c) HNO2
1. The conjugate base of a stong acid has no effect on the pH. Why or...
1. The conjugate base of a stong acid has no effect on the pH. Why or why not? Include a comment on the conjugate acid of a base. 2. Given the discussion of question one above, then if I were to dissolve the following salt, KNO3, in water, what would the resulting pH be and why?
Calculation of Molar Ratios of Conjugate Base to Weak Acid from pH For a weak acid...
Calculation of Molar Ratios of Conjugate Base to Weak Acid from pH For a weak acid with a pKa of 6.0, calculate the ratio of conjugate base to acid at a pH of 5.0. Choice of Weak Acid for a Buffer Which of these com-pounds would be the best buffer at pH 5.0: formic acid (pKa 5 3.8), acetic acid (pKa 5 4.76), or ethylamine (pKa 5 9.0)? Briefly justify your answer. please show work thank you will rate.
3.Write the formula for the conjugate acid of each of the following bases. Base: Conjugate acid:...
3.Write the formula for the conjugate acid of each of the following bases. Base: Conjugate acid: HS− HCO3− CO32− HPO42− SO42− Acid Conjugate base (a) HNO2 (b) H2SO4 (c) H2S (d) HCN (e) HCOOH
ADVERTISEMENT
ADVERTISEMENT
ADVERTISEMENT