$$K_a = 3.7 \times 10$$^{-10}$$

A solution with $$[\mathrm{OH^-}] = 1.0 \times 10$$^{-2}$$\ \mathrm{M}$$

$$[\mathrm{OH^-}] = 1.0 \times 10$$^{-13}$$\ \mathrm{M}$$

$$[\mathrm{H^+}] = 1.0 \times 10$$^{-3}$$\ \mathrm{M}$$

Question 1

Which of the following statements best describes the autoionization of water at 25°C?

Accepted Answer

Water molecules react with each other to form $$\mathrm{H_3O^+}$$ and $$\mathrm{OH^-}$$ ions, with $$K_w = 1.0 	imes 10$$^{-14}$$.

Question 2

A solution has $$[\mathrm{OH^-}] = 6.7 	imes 10$$^{-3}$$\ \mathrm{M} at 25$$°C. What is the pH of the solution?

Accepted Answer

$$pH = 2.83$$

Question 3

Which of the following is true for a strong monoprotic acid in aqueous solution?

Accepted Answer

The concentration of $$\mathrm{H^+}$$ equals the initial concentration of the acid.

Question 4

Calculate the $$K_a$$ for phenol ($$\mathrm{HC_6H_5O}) if a$$ $$0.10\ \mathrm{M}$$ solution has a $$pH of$$ $$5.43 at$$ $$25^\circ\mathrm{C}.$$

Accepted Answer

$$K_a = 3.7 	imes 10$$^{-10}$$

Question 5

Which of the following best explains why $$K_{a1} \u003e K_{a2}$$ for polyprotic acids?

Accepted Answer

It is easier to remove the first proton than the second due to increasing negative charge on the conjugate base.

Question 6

Which of the following solutions is most basic at 25°C?

Accepted Answer

A solution with $$[\mathrm{OH^-}] = 1.0 	imes 10$$^{-2}$$\ \mathrm{M}$$

Question 7

A weak acid, HA, has a $$K_a = 1.8 	imes 10$$^{-5}$$. Which of the following statements is correct?

Accepted Answer

The acid partially ionizes in water and has a conjugate base with $$K_b = 5.6 	imes 10$$^{-10}$$.

Question 8

Which equation correctly relates $$pH$$ and $$pOH at 25$$°C?

Accepted Answer

$$pH + pOH = 14$$

Question 9

A $$0.10\ \mathrm{M}$$ solution of HCl is prepared at $$25^\circ\mathrm{C}. $$What is the $$[\mathrm{OH^-}] in $$the solution?

Accepted Answer

$$[\mathrm{OH^-}] = 1.0 	imes 10$$^{-13}$$\ \mathrm{M}$$

Question 10

Which of the following best describes the relationship between $$K_a$$ and acid strength?

Accepted Answer

A higher $$K_a$$ value indicates a stronger acid.

Question 11

Which of the following is a correct application of the Henderson-Hasselbalch equation?

Accepted Answer

$$pH = pK_a + \log \frac{[A^-]}{[HA]}$$

Question 12

A solution has a $$pH of$$ $$3.0. $$What is the $$[\mathrm{H^+}]$$ concentration?

Accepted Answer

$$[\mathrm{H^+}] = 1.0 	imes 10$$^{-3}$$\ \mathrm{M}$$

Question 13

Which of the following is a property of a strong base?

Accepted Answer

It completely dissociates in water, so $$[\mathrm{OH^-}] = [	ext{base}].$$

Question 14

Which of the following best describes the effect of increasing electronegativity on the acidity of binary acids within the same period?

Accepted Answer

Acidity increases as electronegativity increases.

Question 15

A weak base, B, has a $$K_b = 1.0 	imes 10$$^{-5}$$. What is the K_a$ of its conjugate acid?

Accepted Answer

$$K_a = 1.0 	imes 10$$^{-9}$$

Question 16

Which of the following is the correct formula for percent ionization of a weak acid?

Accepted Answer

$$	ext{Percent Ionization} = \frac{	ext{Concentration of ionized acid}}{	ext{Initial concentration of acid}} 	imes 100\%$$

Question 17

Which of the following methods is the most precise for measuring the pH of a solution?

Accepted Answer

Using a pH meter.

Question 18

Which of the following is true for the $$pH of a $$neutral solution at $$25^\circ\mathrm{C}$$?

Accepted Answer

$$pH = 7.00$$

Question 19

Which of the following best describes the relationship between $$K_a$$, $$K_b$$, and $$K_w$$ for a conjugate acid-base pair?

Accepted Answer

$$K_a 	imes K_b = K_w$$

Acid-Base Equilibria: Core Concepts and Calculations

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