$$\text{Formal Charge} = \text{Valence electrons} - \frac{1}{2}(\text{electrons in bonds}) - \text{non-bonding electrons}$$

Question 1

Which of the following statements best describes the octet rule as it applies to organic molecules?

Accepted Answer

Atoms gain, lose, or share electrons to achieve a stable configuration with 8 valence electrons.

Question 2

What is the electron configuration of a neutral carbon atom?

Accepted Answer

$$1s^2$$ $$2s^2$$ $$2p^2$$

Question 3

Which of the following best explains why water (H$$_2O) is a $$polar molecule?

Accepted Answer

The molecule has a bent shape and the oxygen atom is more electronegative than hydrogen.

Question 4

Which of the following is the correct Lewis structure for the ethyl cation ($$\mathrm{C_2H_5^+}$$)?

Accepted Answer

A structure with two carbon atoms, five hydrogens, and a positive charge on the carbon with only three bonds.

Question 5

Which of the following elements is more electronegative: sulfur (S) or silicon (Si)?

Accepted Answer

Sulfur (S)

Question 6

A molecule has the formula $$\mathrm{C_3H_8O}. $$Which statement is true about its molecular formula?

Accepted Answer

It shows the number of each type of atom but does not provide structural information.

Question 7

Which of the following best describes a resonance structure?

Accepted Answer

A valid Lewis structure that differs only in the position of $$\pi$$ and non-bonding electrons.

Question 8

Which of the following is a correct application of the Pauli Exclusion Principle?

Accepted Answer

No two electrons in the same atom can have the same set of four quantum numbers.

Question 9

Which of the following best explains why the equilibrium in an acid-base reaction lies to the side of the weaker acid?

Accepted Answer

The weaker acid holds the proton more tightly, making the reverse reaction less favorable.

Question 10

Which of the following is a Lewis acid?

Accepted Answer

$$\mathrm{BF_3$}$$

Question 11

Which of the following factors does NOT increase the stability of a conjugate base, and thus does NOT increase acid strength?

Accepted Answer

Placing a negative charge on a less electronegative atom.

Question 12

Which of the following molecules would you expect to have a net dipole moment?

Accepted Answer

$$\mathrm{CH_3F}$$

Question 13

Which of the following is the correct formula for calculating formal charge?

Accepted Answer

$$	ext{Formal Charge} = 	ext{Valence electrons} - \frac{1}{2}(	ext{electrons in bonds}) - 	ext{non-bonding electrons}$$

Question 14

Which of the following best describes the geometry of ammonia ($$\mathrm{NH_3$}) $$according to VSEPR theory?

Accepted Answer

Trigonal pyramidal

Question 15

Which of the following is a constitutional isomer of $$\mathrm{C_2H_6O}$$?

Accepted Answer

Dimethyl ether

Question 16

Which of the following best describes the difference between a Lewis acid and a Bronsted-Lowry acid?

Accepted Answer

A Lewis acid accepts an electron pair, while a Bronsted-Lowry acid donates a proton.

Question 17

Which of the following best explains why $$\mathrm{NaCl}$$ forms an ionic bond?

Accepted Answer

The difference in electronegativity between Na and Cl is greater than 1.7.

Question 18

Which of the following is the best resonance contributor for a molecule with the formula $$\mathrm{NO_2$^-}$$?

Accepted Answer

The structure with the negative charge on the more electronegative oxygen atom.

Question 19

Which of the following factors would make a proton more acidic in a molecule?

Accepted Answer

The conjugate base is stabilized by resonance.

Organic Chemistry Foundations: Atomic Structure, Bonding, Molecular Representations, and Acids/Bases

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