Question 1

Which of the following statements best describes how pKa values can be used to estimate the equilibrium constant ($K_{eq}$) for an acid-base reaction?

Accepted Answer

Subtract the pKa of the base from the pKa of the acid and raise 10 to that power: $K_{eq} = 10^{	ext{pKa}_{	ext{base}} - 	ext{pKa}_{	ext{acid}}}$.

Question 2

Which of the following is the correct definition of a conjugate base?

Accepted Answer

A species formed when an acid loses a proton ($H^+$).

Question 3

Given the acid-base reaction: $CH_3COOH + H_2O \rightarrow CH_3COO^- + H_3O^+$, identify the conjugate acid-base pairs.

Accepted Answer

Conjugate acid: $CH_3COOH$ and $H_3O^+$; Conjugate base: $CH_3COO^-$ and $H_2O$

Question 4

Which of the following is a correct statement about Lewis acids?

Accepted Answer

Lewis acids are electron pair acceptors.

Question 5

Which of the following compounds can act as a Lewis base in an organic reaction?

Accepted Answer

$NH_3$, because it has a lone pair of electrons to donate.

Question 6

A student wants to increase the solubility of benzoic acid in water. Which manipulation would be most effective?

Accepted Answer

Add a strong base to convert benzoic acid to its conjugate base, which is more soluble in water.

Question 7

Which of the following best explains why the ionization state of an organic molecule affects its solubility in water?

Accepted Answer

Ionized molecules are more polar and interact better with water, increasing solubility.

Question 8

Which of the following is the correct product of the acid-base reaction between $NH_3$ and $HCl$?

Accepted Answer

$NH_4^+ + Cl^-$

Question 9

If the pKa of acetic acid is 4.76 and the pKa of water is 15.7, what is the equilibrium constant ($K_{eq}$) for the reaction $CH_3COOH + H_2O \rightarrow CH_3COO^- + H_3O^+$?

Accepted Answer

$K_{eq} = 10^{15.7 - 4.76} = 10^{10.94}$

Question 10

Which of the following statements is true regarding the manipulation of ionization state to change solubility in organic solvents?

Accepted Answer

Deprotonating a carboxylic acid increases its solubility in water but decreases its solubility in organic solvents.

Question 11

Which of the following is the correct conjugate acid of $NH_2^-$?

Accepted Answer

$NH_3$

Question 12

In the reaction $H_2SO_4 + H_2O \rightarrow HSO_4^- + H_3O^+$, which species acts as the acid and which as the base?

Accepted Answer

Acid: $H_2SO_4$; Base: $H_2O$

Question 13

Which of the following is NOT a characteristic of a Lewis base?

Accepted Answer

It accepts an electron pair.

Question 14

A chemist wants to extract a weak organic acid from an aqueous solution into an organic solvent. Which step should they take to maximize extraction?

Accepted Answer

Acidify the solution to convert the acid to its neutral form, increasing its solubility in the organic solvent.

Question 15

Which of the following is the correct conjugate base of $HCO_3^-$?

Accepted Answer

$CO_3^{2-}$

Question 16

Which of the following is a correct application of acid-base theory in predicting solubility?

Accepted Answer

A compound in its ionized form is generally more soluble in water than in organic solvents.

Question 17

Which of the following is the correct product of the acid-base reaction between $HCO_3^-$ and $H_2O$?

Accepted Answer

$CO_3^{2-} + H_3O^+$

Question 18

Which of the following statements best describes the relationship between pKa and acid strength?

Accepted Answer

A lower pKa value indicates a stronger acid.

Question 19

Which of the following is the correct conjugate acid of $H_2O$?

Accepted Answer

$H_3O^+$

Acid-Base Equilibria and Applications in Organic Chemistry

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