Q: Which of the following is the correct formula for calculating the formal charge on an atom in a Lewis structure?

$$\text{Formal charge} = \text{Valence electrons} - (\text{Nonbonding electrons} + \frac{1}{2} \times \text{Bonding electrons})$$

Question 1

Which of the following statements best explains why diamond and graphite, both composed of carbon, have vastly different physical properties?

Accepted Answer

Diamond and graphite have different types of chemical bonds between carbon atoms.

Question 2

Which of the following molecules is expected to have a bent molecular geometry according to VSEPR theory?

Accepted Answer

SO$$_2$$

Question 3

A molecule has four electron groups around its central atom, including one lone pair. What is its expected molecular geometry?

Accepted Answer

Trigonal pyramidal

Question 4

Which of the following best describes a resonance structure?

Accepted Answer

A structure where the distribution of valence electrons differs but atomic connectivity remains the same.

Question 5

Which of the following is NOT a key property of covalent bonds discussed in class?

Accepted Answer

Ionic radius

Question 6

Given the Lewis structure for CO$$_2$$, what is the bond angle between the oxygen atoms?

Accepted Answer

$$180^\circ$$

Question 7

Which of the following molecules is expected to be nonpolar, even though it contains polar bonds?

Accepted Answer

CO$$_2$$

Question 8

What is the formal charge on the central atom in the following Lewis structure of SO$$_3 ($$where all S-O bonds are single bonds and all oxygens have three lone pairs)?

Accepted Answer

+2

Question 9

Which of the following statements about VSEPR theory is correct?

Accepted Answer

VSEPR theory considers the repulsion between electron groups to predict molecular geometry.

Question 10

Which molecule would you expect to have a larger dipole moment: HF or HI? Use electronegativity differences to justify your answer.

Accepted Answer

HF, because fluorine is much more electronegative than hydrogen.

Question 11

A molecule has five electron groups around its central atom, including two lone pairs. What is its molecular geometry?

Accepted Answer

T-shaped

Question 12

Which of the following is an exception to the octet rule?

Accepted Answer

BF$$_3$$

Question 13

Which of the following best explains why O$$_2 is $$paramagnetic, even though Lewis theory predicts all electrons are paired?

Accepted Answer

O$$_2$$ has unpaired electrons due to its molecular orbital structure, which Lewis theory does not account for.

Question 14

Which of the following steps is NOT part of predicting molecular geometry using VSEPR theory?

Accepted Answer

Calculate the atomic mass of the central atom.

Question 15

Which molecule is expected to have a trigonal planar molecular geometry?

Accepted Answer

BF$$_3$$

Question 16

A molecule has six electron groups around its central atom, with two lone pairs. What is its molecular geometry?

Accepted Answer

Square planar

Question 17

Which of the following molecules is expected to be polar due to its molecular geometry?

Accepted Answer

NH$$_3$$

Question 18

Which factor does NOT contribute to distortions from ideal molecular geometry?

Accepted Answer

Atomic number of the central atom

Question 19

Which of the following is the correct formula for calculating the formal charge on an atom in a Lewis structure?

Accepted Answer

$$	ext{Formal charge} = 	ext{Valence electrons} - (	ext{Nonbonding electrons} + \frac{1}{2} 	imes 	ext{Bonding electrons})$$

Question 20

Which of the following statements about molecular polarity is correct?

Accepted Answer

A molecule is polar if it has polar bonds and the vector sum of the bond dipole moments is nonzero.

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