Q: What are $$[H^+]$$, $$[A^-]$$, and $$[B^-] in a $$solution that contains 0.03 M $$HA$$ and 0.1 M $$HB$$? $$K_a$$ for $$HA$$ and $$HB$$ are $$1.0 \times 10$$^{-5}$$ and 1.0$$ \times $$10^{-6}$$ respectively.

$$[H^+] = 1.0 \times 10$$^{-5}$$ M, $$[A^-] = 3.0 \times $$10^{-3} M$$, $$[B^-] = 1.0 \times 10$$^{-6}$$ M

Question 1

For ortho phosphoric acid, which of the following correctly represents the relationship between its dissociation constants $$K_a$$, $$K_{a1}$$, $$K_{a2}$$, and $$K_{a3}$$?

Accepted Answer

$$K_{a1} \u003e K_{a2} \u003e K_{a3}$$

Question 2

A solution contains 0.1 M $$H_3PO_4 ($$phosphoric acid). Given $$K_{a1} = 7.5 	imes 10$$^{-3}$$, what is the approximate concentration of H$$^+$$ ions in the solution?

Accepted Answer

$$0.027 M$$

Question 3

In a solution of 0.1 M $$H_3PO_4$$, what is the concentration of $$PO_4$$^{3-}$$ ions? (K$$_{a3} = 4.2 	imes $$10^{-13})$$

Accepted Answer

$$1.0 	imes 10$$^{-12}$$ M

Question 4

Which of the following is true regarding the $$OH^-$$ ions produced from the second ionization of weak polyacidic bases in aqueous solution?

Accepted Answer

Their concentration is negligible compared to the first ionization.

Question 5

The dissociation constant of acetic acid at a given temperature is $$1.69 	imes 10$$^{-5}$$. The degree of dissociation of 0.01 M acetic acid in the presence of 0.01 M $$NaOH$$ is:

Accepted Answer

$$2.9 	imes 10$$^{-2}$$

Question 6

A 0.01 M solution of $$NH_4Cl is $$mixed with 0.01 M $$NH_4OH. $$What is the resulting pH if $$K_b$$ for $$NH_4OH is$$ $$1.8 	imes 10$$^{-5}$$?

Accepted Answer

$$9.25$$

Question 7

Which of the following statements is correct regarding the hydrolysis of $$Na_2CO_3 in $$water?

Accepted Answer

The solution will be basic due to $$CO_3$$^{2-}$$ hydrolysis.

Question 8

For a $$BCl_2$$ solution (chloride salt of a diacidic base $$B$$), which expression gives the dissociation constant of the base?

Accepted Answer

$$K_b = \dfrac{K_w}{K_{a2}}$$

Question 9

At $$25^\circC$$, $$K_b$$ for $$BOH is$$ $$1.0 	imes 10$$^{-2}$$. A 0.01 M solution of $$BOH$$ has what value of $$[OH^-]$$?

Accepted Answer

$$1.0 	imes 10$$^{-2}$$ M

Question 10

Which of the following is independent of its concentration?

Accepted Answer

The pH of a salt solution

Question 11

Consider an aqueous solution containing 0.1 M each of $$HCOOH$$, $$CH_3COOH$$, $$COOH$$, and $$H_3PO_4. $$Which of the following is true regarding the $$[H^+]$$ concentration?

Accepted Answer

It is the sum of $$[H^+]$$ released by the first dissociation of all the acids.

Question 12

What are $$[H^+]$$, $$[A^-]$$, and $$[B^-] in a $$solution that contains 0.03 M $$HA$$ and 0.1 M $$HB$$? $$K_a$$ for $$HA$$ and $$HB$$ are $$1.0 	imes 10$$^{-5}$$ and 1.0$$ 	imes $$10^{-6}$$ respectively.

Accepted Answer

$$[H^+] = 1.0 	imes 10$$^{-5}$$ M, $$[A^-] = 3.0 	imes $$10^{-3} M$$, $$[B^-] = 1.0 	imes 10$$^{-6}$$ M

Question 13

Which statement is correct regarding the hydrolysis of $$NH_4Cl in $$water?

Accepted Answer

The solution will be acidic due to $$NH_4$$^+$$ hydrolysis.

Question 14

Which of the following is the correct expression for the hydrolysis constant $$K_h of a $$salt of a weak acid and strong base?

Accepted Answer

$$K_h = \dfrac{K_w}{K_a}$$

Question 15

A solution is prepared by mixing 0.1 M $$H_2SO_4$$ and 0.1 M $$NaOH. $$What is the resulting pH?

Accepted Answer

$$1.26$$

Question 16

Which of the following is true about the effect of common ion on the dissociation of a weak acid?

Accepted Answer

It decreases the degree of dissociation.

Question 17

Which of the following is the correct relationship for the dissociation constant of a base $$K_b in $$terms of $$K_w$$ and $$K_a$$?

Accepted Answer

$$K_b = \dfrac{K_w}{K_a}$$

Question 18

Which of the following statements is correct regarding the pH of a buffer solution?

Accepted Answer

It depends on the concentration of acid and conjugate base.

Question 19

Which of the following is true for the hydrolysis of $$Na_2SO_4 in $$water?

Accepted Answer

The solution will be neutral.

Acid-Base Equilibria and Buffer Solutions: Study Notes for Organic Chemistry

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