Question 1

Which of the following statements best explains why hydrofluoric acid (HF) is a stronger acid than water (H$_2$O)?

Accepted Answer

HF has a lower pKa than water, indicating it donates protons more readily.

Question 2

Consider the halide ions F$^-$, Cl$^-$, Br$^-$, and I$^-$. Which factor most strongly influences their basicity?

Accepted Answer

The size of the ion and the concentration of negative charge on its surface.

Question 3

Which of the following molecules is considered a superacid and is only observed in the gas phase?

Accepted Answer

SbF$_6$

Question 4

Given the following pKa values: HF ($pKa = 3.2$), H$_2$O ($pKa = 15.74$), NH$_3$ ($pKa = 38$), which compound is the strongest acid?

Accepted Answer

HF

Question 5

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

Accepted Answer

Acidity increases as the percent s-character increases in the hybrid orbital.

Question 6

A student is comparing the basicity of F$^-$ and I$^-$. Which statement is true regarding their basicity?

Accepted Answer

F$^-$ is a stronger base than I$^-$ because its negative charge is concentrated on a smaller surface area.

Question 7

Which of the following best describes an amphoteric substance?

Accepted Answer

A substance that can act as either an acid or a base.

Question 8

Which of the following carbon hybridizations corresponds to the highest acidity?

Accepted Answer

sp

Question 9

If a molecule has a pKa of $-10$, what can be inferred about its acid strength?

Accepted Answer

It is a very strong acid.

Question 10

Which of the following factors does NOT directly affect the strength of acids and bases?

Accepted Answer

The number of protons in the nucleus.

Question 11

A chemist is choosing a nucleophile for a reaction with CH$_3$I. Which halide ion would be most effective, based on polarizability?

Accepted Answer

I$^-$

Question 12

Which of the following acids has the lowest pKa and is therefore the strongest acid?

Accepted Answer

H$_2$SO$_4$

Question 13

Which statement best explains why sp hybridized carbons are more acidic than sp$^3$ hybridized carbons?

Accepted Answer

sp hybridized carbons have higher s-character, stabilizing the negative charge on the conjugate base.

Question 14

Which of the following is the weakest acid based on its pKa value?

Accepted Answer

CH$_4$ ($pKa = 50$)

Question 15

Which of the following statements about conjugate bases is correct?

Accepted Answer

The conjugate base of a strong acid is a weak base.

Question 16

A molecule with a pKa of $-1.74$ is most likely to:

Accepted Answer

Donate a proton easily, acting as a strong acid.

Question 17

Which of the following best describes the relationship between nucleophilicity and polarizability among halide ions?

Accepted Answer

Nucleophilicity increases as polarizability increases.

Question 18

Which of the following is true regarding the trend in acidity for the hydrogen halides (HF, HCl, HBr, HI)?

Accepted Answer

Acidity increases as you move down the group from HF to HI.

Question 19

Which of the following statements about the relationship between pKa and acid strength is correct?

Accepted Answer

A lower pKa value indicates a stronger acid.

Question 20

A compound is described as highly unstable and only observed in the gas phase. What does this suggest about its acid strength?

Accepted Answer

It is a superacid with extremely low pKa.

Acids, Bases, and Factors Affecting Their Strength in Organic Chemistry

Study Guide - Practice Questions