Hypoiodous acid ($\mathrm{HIO}$), $K_a = 2.3 \times 10^{-11}$

Question 1

Which of the following best explains why HBr is a stronger acid than HF?

Accepted Answer

Bromine is less electronegative than fluorine, making the H-Br bond weaker and easier to ionize.

Question 2

As you move down a group in the periodic table, what is the general trend in acid strength for binary acids (e.g., HCl, HBr, HI)?

Accepted Answer

Acid strength increases because the H-X bond becomes weaker.

Question 3

Which of the following compounds is most likely to act as a weak base due to the presence of a lone pair on nitrogen?

Accepted Answer

Methylamine ($\mathrm{CH_3NH_2}$)

Question 4

Which of the following best describes the trend in acid strength for the oxyacids $\mathrm{HClO}$, $\mathrm{HBrO}$, and $\mathrm{HIO}$?

Accepted Answer

Acid strength decreases as the electronegativity of Y decreases.

Question 5

Which of the following statements is true regarding the acid-base behavior of ammonia ($\mathrm{NH_3}$) and phosphine ($\mathrm{PH_3}$)?

Accepted Answer

$\mathrm{NH_3}$ is a stronger base than $\mathrm{PH_3}$ because nitrogen is more electronegative and holds its lone pair less tightly.

Question 6

Which of the following best explains why $\mathrm{H_2SO_4}$ (sulfuric acid) is a stronger acid than $\mathrm{H_2SO_3}$ (sulfurous acid)?

Accepted Answer

$\mathrm{H_2SO_4}$ has more oxygen atoms, which stabilize the conjugate base through resonance.

Question 7

Which of the following amines would you expect to be the strongest base?

Accepted Answer

Methylamine ($\mathrm{CH_3NH_2}$)

Question 8

Given the following dissociation constants, which acid is the weakest?

Accepted Answer

Hypoiodous acid ($\mathrm{HIO}$), $K_a = 2.3 	imes 10^{-11}$

Question 9

Which of the following best explains why the conjugate base of a strong acid is a weak base?

Accepted Answer

The conjugate base is very stable and has little tendency to accept a proton.

Question 10

Which of the following best describes the structural feature common to all amines that makes them basic?

Accepted Answer

A lone pair of electrons on the nitrogen atom.

Question 11

Which of the following bases has the largest value for $K_b$ based on the relative stability of their conjugate acids?

Accepted Answer

$\mathrm{CH_3NH_2}$

Question 12

Which of the following statements is true regarding the acid strength of $\mathrm{HF}$, $\mathrm{HCl}$, and $\mathrm{HBr}$?

Accepted Answer

$\mathrm{HBr}$ > $\mathrm{HCl}$ > $\mathrm{HF}$

Question 13

Which of the following best explains why $\mathrm{CH_4}$ is neither an acid nor a base?

Accepted Answer

Carbon is not electronegative enough to polarize the C-H bond and does not have a lone pair.

Question 14

Which of the following is the strongest acid?

Accepted Answer

$\mathrm{HCl}$

Question 15

Which of the following best explains why the acid strength of oxyacids increases with the number of oxygen atoms attached to the central atom?

Accepted Answer

Additional oxygen atoms increase the electron-withdrawing effect, stabilizing the conjugate base.

Chemical Structure and Acid-Base Behavior: Predicting Strength from Molecular Structure

Study Guide - Practice Questions