Question 1

Which statement best explains why ionic compounds like NaCl have high melting points?

Accepted Answer

Because the electrostatic attraction between oppositely charged ions is very strong, requiring a lot of energy to break.

Question 2

In the molecular orbital model for dihydrogen ($$\mathrm{H}_2$$), what is the main difference between the bonding and antibonding orbitals?

Accepted Answer

Bonding orbitals result from in-phase overlap and stabilize the molecule, while antibonding orbitals result from out-of-phase overlap and destabilize the molecule.

Question 3

Which of the following molecules has a trigonal planar geometry?

Accepted Answer

Formaldehyde ($$\mathrm{CH}_2O)$$

Question 4

Given the following electronegativities: $$\mathrm{H} = 2.3$$, $$\mathrm{C} = 2.5$$, $$\mathrm{N} = 3.0$$, $$\mathrm{O} = 3.5$$, which bond is expected to be the most polar?

Accepted Answer

$$\mathrm{O-H}$$

Question 5

Which of the following best describes the process of drawing a line-angle structure in organic chemistry?

Accepted Answer

Carbon atoms are represented by the ends and bends of lines, hydrogens attached to carbons are inferred, and only heteroatoms and their hydrogens are explicitly drawn.

Question 6

Which of the following is a correct rule for resonance structures?

Accepted Answer

The number of electrons and net charge must remain the same in all resonance contributors.

Question 7

Which resonance contributor is considered the major contributor?

Accepted Answer

The one that satisfies the octet rule and places negative charges on the most electronegative atoms.

Question 8

Which curved arrow in a reaction mechanism represents the movement of electrons from a lone pair to form a new bond?

Accepted Answer

An arrow starting at a lone pair and ending at an atom or bond.

Question 9

Which of the following statements about Bronsted acids and bases is correct?

Accepted Answer

A Bronsted acid is a proton donor and a Bronsted base is a proton acceptor.

Question 10

Given the following $$pK_a$$ values: $$\mathrm{HBr} = -8$$, $$\mathrm{H}_2O = 15.7$$, $$\mathrm{HCN} = 9.3$$, which is the strongest acid?

Accepted Answer

$$\mathrm{HBr}$$

Question 11

Which factor most accurately predicts acid strength among elements in the same period?

Accepted Answer

Electronegativity

Question 12

Which environmental effect increases the acidity of a molecule?

Accepted Answer

Placing electron-withdrawing groups near the conjugate base anion.

Question 13

For the acid-base equilibrium $$\mathrm{CH}_3COOH + \mathrm{NH}_3 \rightleftharpoons \mathrm{CH}_3COO^- + \mathrm{NH}_4^+$$, given $$pK_a$$ values $$\mathrm{CH}_3COOH = 4.7$$ and $$\mathrm{NH}_4^+ = 9.3$$, which direction does the equilibrium favor?

Accepted Answer

Toward products ($$\mathrm{CH}_3COO^- + \mathrm{NH}_4^+)$$

Question 14

Which of the following is a Lewis acid?

Accepted Answer

A molecule that accepts a pair of electrons

Question 15

What is the formal charge on the nitrogen atom in the molecule $$\mathrm{H}_2N{-}CH_3$?

Accepted Answer

$$0$$

Question 16

Which of the following molecules is nonpolar despite having polar bonds?

Accepted Answer

Carbon dioxide ($$\mathrm{CO}_2)$$

Question 17

Which step is NOT part of the systematic rules for drawing a Lewis structure?

Accepted Answer

Changing the atomic connectivity to minimize formal charges

Question 18

Which of the following best explains why $$\mathrm{H}_2O$$ has a bond angle less than $$109.5^\circ$$?

Accepted Answer

Because lone pairs on oxygen repel the bonded pairs more strongly, reducing the bond angle.

Question 19

Which of the following is the correct order of acid strength from weakest to strongest for the following acids: $$\mathrm{HF}$$, $$\mathrm{HCl}$$, $$\mathrm{HBr}$$, $$\mathrm{HI}$$?

Accepted Answer

$$\mathrm{HF} \u003c \mathrm{HCl} \u003c \mathrm{HBr} \u003c \mathrm{HI}$$

Fundamental Concepts in Organic Chemistry: Atomic Structure, Bonding, and Molecular Geometry

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