Q: A 0.10 M solution of acetic acid ($$\mathrm{CH}_3\mathrm{COOH}) $$has a $$K_a = 1.8 \times 10$$^{-5}$$. What is the equilibrium concentration of $$\mathrm{H}_3\mathrm{O}^+$$?

$$[\mathrm{H}_3\mathrm{O}^+] = 1.34 \times 10$$^{-3}$$\ \mathrm{M}$$

Q: If the $$[\mathrm{H}_3\mathrm{O}^+] in a $$solution is $$2.12 \times 10$$^{-3}$$\ \mathrm{M}$$, what is the pH of the solution?

$$\mathrm{pH} = -\log(2.12 \times 10$$^{-3}$$) = 2.67$$

Q: A 0.25 M solution of ammonia ($$\mathrm{NH}_3) $$has a $$K_b = 1.8 \times 10$$^{-5}$$. What is the equilibrium concentration of $$\mathrm{OH}^-$$?

$$[\mathrm{OH}^-] = 2.12 \times 10$$^{-3}$$\ \mathrm{M}$$

Q: A solution has $$[\mathrm{OH}^-] = 7.41 \times 10$$^{-12}$$\ \mathrm{M}. $$What is the pOH of the solution?

$$\mathrm{pOH} = -\log(7.41 \times 10$$^{-12}$$) = 11.13$$

Question 1

Which of the following statements best describes the relationship between pH and pOH in aqueous solutions at 25°C?

Accepted Answer

$$\mathrm{pH} + \mathrm{pOH} = 14.00$$

Question 2

A 0.15 M solution of hydrochloric acid (HCl) is prepared. What is the pH of the solution?

Accepted Answer

$$\mathrm{pH} = -\log(0.15) = 0.82$$

Question 3

Which of the following acids is classified as a diprotic acid?

Accepted Answer

H$$_2SO$_4$$

Question 4

What is the hydroxide ion concentration $$[\mathrm{OH}^-] in a 0.15 M $$solution of barium hydroxide, Ba(OH)$$_2$$?

Accepted Answer

$$[\mathrm{OH}^-] = 0.30\ \mathrm{M}$$

Question 5

A 0.10 M solution of acetic acid ($$\mathrm{CH}_3\mathrm{COOH}) $$has a $$K_a = 1.8 	imes 10$$^{-5}$$. What is the equilibrium concentration of $$\mathrm{H}_3\mathrm{O}^+$$?

Accepted Answer

$$[\mathrm{H}_3\mathrm{O}^+] = 1.34 	imes 10$$^{-3}$$\ \mathrm{M}$$

Question 6

Which of the following best explains why the calculation of pH for a polyprotic acid like H$$_3PO$_4 is $$more complex than for a monoprotic acid?

Accepted Answer

Polyprotic acids dissociate in multiple, sequential steps, each with its own equilibrium, requiring multiple ICE tables.

Question 7

If the $$[\mathrm{H}_3\mathrm{O}^+] in a $$solution is $$2.12 	imes 10$$^{-3}$$\ \mathrm{M}$$, what is the pH of the solution?

Accepted Answer

$$\mathrm{pH} = -\log(2.12 	imes 10$$^{-3}$$) = 2.67$$

Question 8

A 0.25 M solution of ammonia ($$\mathrm{NH}_3) $$has a $$K_b = 1.8 	imes 10$$^{-5}$$. What is the equilibrium concentration of $$\mathrm{OH}^-$$?

Accepted Answer

$$[\mathrm{OH}^-] = 2.12 	imes 10$$^{-3}$$\ \mathrm{M}$$

Question 9

Which of the following is a correct expression for the acid dissociation constant ($$K_a) $$for the reaction $$\mathrm{CH}_3\mathrm{COOH} + \mathrm{H}_2\mathrm{O} \rightleftharpoons \mathrm{H}_3\mathrm{O}^+ + \mathrm{CH}_3\mathrm{COO}^-$$?

Accepted Answer

$$K_a = \dfrac{[\mathrm{H}_3\mathrm{O}^+][\mathrm{CH}_3\mathrm{COO}^-]}{[\mathrm{CH}_3\mathrm{COOH}]}$$

Question 10

Which of the following is a property of a strong acid in aqueous solution?

Accepted Answer

It completely ionizes in water.

Question 11

A solution has $$[\mathrm{OH}^-] = 7.41 	imes 10$$^{-12}$$\ \mathrm{M}. $$What is the pOH of the solution?

Accepted Answer

$$\mathrm{pOH} = -\log(7.41 	imes 10$$^{-12}$$) = 11.13$$

Question 12

Which of the following best describes a triprotic acid?

Accepted Answer

An acid that can donate three protons in solution, such as $$\mathrm{H}_3\mathrm{PO}_4$$

Question 13

A 0.10 M solution of phosphoric acid ($$\mathrm{H}_3\mathrm{PO}_4) $$has $$K_{a1} = 7.5 	imes 10$$^{-3}$$. What is the $$[\mathrm{H}_3\mathrm{O}^+]$$ at equilibrium for the first dissociation step?

Accepted Answer

$$[\mathrm{H}_3\mathrm{O}^+] = 0.024\ \mathrm{M}$$

Question 14

Which of the following is true about the dissociation of weak bases in water?

Accepted Answer

The $$K_b$$ value describes the degree of dissociation for a base.

Question 15

A solution has a pH of 1.62. What is the $$[\mathrm{H}_3\mathrm{O}^+]$$ concentration?

Accepted Answer

$$[\mathrm{H}_3\mathrm{O}^+] = 10$$^{-1.62}$$ = 0.024\ \mathrm{M}$$

Question 16

Which of the following is a correct statement about the $$K_a$$ value of an acid?

Accepted Answer

A larger $$K_a$$ value means the acid is stronger.

Question 17

Which of the following best describes a monoprotic acid?

Accepted Answer

An acid that can donate only one proton per molecule, such as HCl

Question 18

A solution has a pOH of 0.52. What is the $$[\mathrm{OH}^-]$$ concentration?

Accepted Answer

$$[\mathrm{OH}^-] = 10$$^{-0.52}$$ = 0.30\ \mathrm{M}$$

Acid-Base Equilibria and Measuring Acidity: General Chemistry Study Notes

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