Question 1

Which of the following statements best describes the relationship between acid strength and the stability of its conjugate base?

Accepted Answer

The stronger the acid, the more stable its conjugate base.

Question 2

Given the following reaction: $$\mathrm{CH_3COOH} + \mathrm{NH_3$} \rightleftharpoons \mathrm{CH_3COO^-} + \mathrm{NH_4$^+}$$, use the provided $$pK_a$$ values ($$pK_a of $$acetic acid = 4.8, $$pK_a of $$ammonium ion = 9.4) to calculate the equilibrium constant $$K_{eq}$$ for the reaction.

Accepted Answer

$$K_{eq} = 10$$^{-4.6}$$

Question 3

Which of the following compounds is the strongest acid? Use the $$pK_a$$ values: methyl alcohol ($$pK_a = 15.5$$), acetic acid ($$pK_a = 4.76$$), methylamine ($$pK_a = 40$$), and ammonia ($$pK_a = 36).$$

Accepted Answer

Acetic acid

Question 4

Which factor most directly explains why carboxylic acids are stronger acids than alcohols?

Accepted Answer

Carboxylic acids have resonance stabilization of their conjugate base.

Question 5

Which of the following statements about the effect of substituents on acid strength is correct?

Accepted Answer

An electronegative substituent close to the acidic proton increases acid strength.

Question 6

Which of the following species is neutral in its acidic form and charged in its basic form?

Accepted Answer

Carboxylic acid

Question 7

According to the Henderson-Hasselbalch equation, what is the ratio of basic to acidic form when $$pH = pK_a + 2$$?

Accepted Answer

100:1

Question 8

Which of the following is a correct application of the Brønsted-Lowry definition of acids and bases?

Accepted Answer

An acid is a species that loses a proton.

Question 9

Which of the following factors increases the acidity of a compound?

Accepted Answer

Increasing atomic size of the atom bonded to hydrogen.

Question 10

Which of the following is the strongest acid? Consider the following $$pK_a$$ values: $$HF$$ ($$pK_a = 3.2$$), $$H_2O$$ ($$pK_a = 15.7$$), $$NH_3$$ ($$pK_a = 36$$), $$CH_4$$ ($$pK_a = 50).$$

Accepted Answer

$$HF$$

Question 11

Which of the following statements about the position of equilibrium in acid-base reactions is correct?

Accepted Answer

Equilibrium favors formation of the weaker acid.

Question 12

Which of the following is a Lewis acid?

Accepted Answer

$$AlCl_3$$

Question 13

Which of the following best explains why methyl alcohol ($$CH_3OH) is a $$stronger acid than methylamine ($$CH_3NH_2$$)?

Accepted Answer

Oxygen is more electronegative than nitrogen.

Question 14

Which of the following species has delocalized electrons in its conjugate base?

Accepted Answer

$$CH_3COO^-$$

Question 15

Which of the following statements about hybridization and acidity is correct?

Accepted Answer

An sp-hybridized atom is more electronegative than an sp$$^3-$$hybridized atom.

Question 16

A buffer solution is best prepared using which of the following combinations?

Accepted Answer

A weak acid and its conjugate base.

Question 17

Which of the following is the conjugate acid of $$NH_3$$?

Accepted Answer

$$NH_4$$^+$$

Question 18

Which of the following is the conjugate base of $$H_2O$$?

Accepted Answer

$$OH^-$$

Question 19

Which of the following is true about the $$pK_a$$ value of a strong acid?

Accepted Answer

A strong acid has a small $$pK_a$$ value.

Question 20

Which of the following is the correct formula for calculating $$pH$$?

Accepted Answer

$$pH = -\log[H^+]$$

Acids and Bases: Central Concepts in Organic Chemistry

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