Question 1

Which of the following best describes the bond order and resonance in the phosphate ion ($$\mathrm{PO_4$^{3-}}) as $$shown in the Lewis structures above?

Accepted Answer

All four P–O bonds are equivalent due to resonance, with a bond order between 1 and 2.

Question 2

How many sigma ($$\sigma) $$and pi ($$\pi) $$bonds are present in the molecule represented by the structure with labels 1, 2, and 3 (see last image)?

Accepted Answer

7 $$\sigma$$, 1 $$\pi$$

Question 3

What is the hybridization of the atom labeled 1 in the last image (the carbonyl carbon)?

Accepted Answer

$$sp^2$$

Question 4

Which Lewis structure for $$\mathrm{PO_4$^{3-}} ($$see images 1–5) best represents the actual structure of the ion?

Accepted Answer

The structure with one double bond and three single bonds, with lone pairs distributed to minimize formal charge.

Question 5

What is the formal charge on the phosphorus atom in the best Lewis structure for $$\mathrm{PO_4$^{3-}}$$?

Accepted Answer

+1

Question 6

In the molecule shown in the last image, what is the hybridization of the atom labeled 2 (the central carbon)?

Accepted Answer

$$sp^3$$

Question 7

Which of the following statements about resonance in $$\mathrm{PO_4$^{3-}} is $$correct?

Accepted Answer

Resonance structures indicate that the actual structure is a hybrid with delocalized electrons.

Question 8

For the nitrogen atom labeled 3 in the last image, what is its electron geometry and hybridization?

Accepted Answer

Tetrahedral, $$sp^3$$

Question 9

Which of the following best explains why all P–O bonds in $$\mathrm{PO_4$^{3-}}$$ are the same length experimentally?

Accepted Answer

Because resonance delocalizes the electrons, making all bonds equivalent.

Question 10

Which of the following is the correct total number of valence electrons in $$\mathrm{PO_4$^{3-}}$$?

Accepted Answer

32

Question 11

If you were to replace one oxygen atom in $$\mathrm{PO_4$^{3-}}$$ with a sulfur atom, what would be the effect on the bond angles around phosphorus?

Accepted Answer

The bond angles would become slightly less than $$109.5^\circ$$ due to the larger size of sulfur.

Question 12

Which of the following best describes the molecular geometry of $$\mathrm{PO_4$^{3-}}$$?

Accepted Answer

Tetrahedral

Question 13

In the molecule shown in the last image, which atom is most likely to have a lone pair?

Accepted Answer

Atom 3 (nitrogen)

Question 14

Which of the following is a correct statement about the formal charges in the best Lewis structure for $$\mathrm{PO_4$^{3-}}$$?

Accepted Answer

One oxygen atom has a formal charge of 0, and three have -1.

General Chemistry Exam Study Guide: Bonding, Lewis Structures, and Molecular Geometry

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