Question 1

Which atom in the following structure has a formal charge, and what is its value?

$$\ce{O=C=O}$$

Accepted Answer

All atoms have a formal charge of $$0.$$

Question 2

Which of the following is the correct resonance structure for the nitrite ion, $$\ce{NO2^-}$$?

Accepted Answer

Both $$\ce{O=N-O^-}$$ and $$\ce{^-O-N=O}$$

Question 3

Which of the following best explains why the hydrogen atom in acetic acid ($$\ce{CH3COOH}) is $$more acidic than the hydrogen atoms in ethanol ($$\ce{CH3CH2OH}$$)?

Accepted Answer

The conjugate base of acetic acid is stabilized by resonance.

Question 4

Given the following acid-base reaction, which species acts as the conjugate base?

$$\ce{H2O + CH3O^- -\u003e HO^- + CH3OH}$$

Accepted Answer

$$\ce{HO^-}$$

Question 5

Which of the following statements about resonance structures is correct?

Accepted Answer

The actual molecule is a hybrid of all resonance structures.

Question 6

What is the formal charge on the nitrogen atom in $$\ce{NO3^-} ($$nitrate ion)?

Accepted Answer

$$0$$

Question 7

Which of the following best describes the role of resonance in stabilizing the acetate ion ($$\ce{CH3COO^-}$$)?

Accepted Answer

Resonance delocalizes the negative charge over two oxygen atoms.

Question 8

Which of the following is the correct mechanism for the acid-base reaction between water and methoxide ion ($$\ce{CH3O^-}$$)?

Accepted Answer

The lone pair on $$\ce{O} in$$ $$\ce{CH3O^-}$$ attacks the hydrogen in $$\ce{H2O}$$, forming $$\ce{CH3OH}$$ and $$\ce{OH^-}.$$

Question 9

Which of the following is the strongest acid in water?

Accepted Answer

$$\ce{CH3COOH} ($$acetic acid)

Question 10

Which of the following best explains why the negative charge in the acetate ion is more stable than in the ethoxide ion?

Accepted Answer

The negative charge in acetate is delocalized by resonance.

Question 11

What is the formal charge on the oxygen atom in $$\ce{H3O^+}$$?

Accepted Answer

$$+1$$

Question 12

Which of the following is NOT a valid resonance structure for $$\ce{CO3$$^{2-}$$} ($$carbonate ion)?

Accepted Answer

A structure with all single bonds and three negative charges on the oxygens.

Question 13

Which of the following statements about formal charge is correct?

Accepted Answer

Formal charge is calculated by assuming equal sharing of electrons in bonds.

Question 14

In the reaction $$\ce{H2O + CH3O^- -\u003e HO^- + CH3OH}$$, which species is the conjugate acid?

Accepted Answer

$$\ce{CH3OH}$$

Question 15

Which of the following best describes the effect of resonance on acidity?

Accepted Answer

Resonance increases acidity by stabilizing the conjugate base.

Study Guide: Formal Charge, Resonance, and Acidity in Organic Chemistry

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