Question 1

Which of the following statements best explains why carboxylic acids have higher boiling points than alcohols of similar molecular weight?

Accepted Answer

Carboxylic acids form stronger hydrogen bonds due to the presence of two electronegative oxygen atoms, allowing them to dimerize.

Question 2

Which of the following is the correct IUPAC name for the compound with the structure $$\mathrm{HOOC{-}CH_2${-}CH_2${-}COOH}$$?

Accepted Answer

Butanedioic acid

Question 3

A drug has a carboxylic acid functional group and a long hydrocarbon chain (10 carbons). Which statement best describes its solubility in water?

Accepted Answer

It is mostly insoluble due to the large hydrophobic alkyl chain.

Question 4

Which of the following acids is stronger, and why? Acetic acid ($$\mathrm{CH_3COOH}$$, $$pK_a = 4.7) or $$chloroacetic acid ($$\mathrm{ClCH_2COOH}$$, $$pK_a = 2.7$$)?

Accepted Answer

Chloroacetic acid, because its lower $$pK_a$$ indicates greater acidity.

Question 5

Given the following functional groups, which has the highest priority in IUPAC nomenclature?

Accepted Answer

Carboxylic acid

Question 6

Which of the following equations correctly represents the Henderson-Hasselbalch equation for a weak acid?

Accepted Answer

$$pH = pK_a + \log_{10} \frac{[A^-]}{[HA]}$$

Question 7

A solution contains 0.1 M acetic acid ($$pK_a = 4.7) $$and 0.1 M sodium acetate. What is the pH of the solution?

Accepted Answer

$$pH = 4.7$$

Question 8

Which of the following best explains why carboxylate ions are more stable than alkoxide ions?

Accepted Answer

The negative charge in carboxylate ions is delocalized over two oxygen atoms.

Question 9

Aspirin is an acidic drug with $$pK_a = 3.6. $$Calculate the percentage of ionisation in the stomach at $$pH = 2.0. ($$Use $$\%\ 	ext{ionisation} = \frac{[	ext{dissoc}]}{[	ext{undissoc}] + [	ext{dissoc}]} 	imes 100\%$$ and $$\log_{10} x = y \implies x = 10^y)$$

Accepted Answer

2.44\%

Question 10

Which of the following drugs is most likely to be absorbed in the stomach (pH 1-3)?

Accepted Answer

A weak acid in its unionised form

Question 11

Which of the following is the correct expression for the acid dissociation constant $$K_a$$ for a carboxylic acid $$RCOOH in $$water?

Accepted Answer

$$K_a = \frac{[RCOO^-][H_3O^+]}{[RCOOH]}$$

Question 12

Which of the following carboxylic acids is most soluble in water?

Accepted Answer

Methanoic acid

Question 13

Which of the following is the correct common name for ethanoic acid?

Accepted Answer

Acetic acid

Question 14

A basic drug has $$pK_a = 8.6. At$$ $$pH = 9.0$$, what is the percentage of ionisation? (Use $$\%\ 	ext{ionisation} = 100\% - \%\ 	ext{dissociation}$$, $$\%\ 	ext{dissociation} = \frac{[	ext{dissoc}]}{[	ext{undissoc}] + [	ext{dissoc}]} 	imes 100\%$$, and $$\log_{10} x = y \implies x = 10^y)$$

Accepted Answer

28.47\%

Question 15

Which of the following best describes the effect of increasing the length of the hydrocarbon chain in a carboxylic acid on its water solubility?

Accepted Answer

Water solubility decreases due to the larger hydrophobic region.

Question 16

Which of the following is the correct IUPAC name for the compound with the structure $$\mathrm{C_6H_5COOH}$$?

Accepted Answer

Benzoic acid

Question 17

Which of the following statements about drug partitioning is correct?

Accepted Answer

Only the unionised (uncharged) form of a drug can cross biological membranes.

Question 18

Which of the following is the correct relationship between $$pK_a$$ and acid strength?

Accepted Answer

The smaller the $$pK_a$$, the stronger the acid.

Question 19

Which of the following is the correct symbolic name for 2-bromopropanoic acid?

Accepted Answer

$$\alpha-$$bromopropionic acid

Carboxylic Acids: Structure, Properties, and Ionization

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