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

$$\text{Formal charge} = \text{Number of valence electrons} - (\text{Number of unshared electrons} + \frac{1}{2} \times \text{Number of shared electrons})$$

Question 1

Which of the following statements best explains why carbon forms four covalent bonds in most of its compounds?

Accepted Answer

Carbon has four valence electrons and needs four more to complete its octet, so it forms four covalent bonds by sharing electrons.

Question 2

What is the electron configuration of silicon in its ground state?

Accepted Answer

$$1s^2$$\ $$2s^2$$\ $$2p^6$$\ $$3s^2$$\ $$3p^2$$

Question 3

Which of the following molecules contains a polar covalent bond but is overall nonpolar?

Accepted Answer

Carbon tetrachloride ($$CCl_4)$$

Question 4

According to the VSEPR theory, what is the bond angle in methane ($$CH_4$$)?

Accepted Answer

$$109.5^\circ$$

Question 5

Which of the following best describes the hybridization of the central atom in formaldehyde ($$CH_2O$$)?

Accepted Answer

sp$$^2$$

Question 6

Which of the following functional groups is present in acetic acid?

Accepted Answer

Carboxyl group ($$-COOH)$$

Question 7

Which of the following statements about resonance structures is FALSE?

Accepted Answer

Resonance structures can have different numbers of atoms.

Question 8

Which of the following molecules is expected to have the largest dipole moment?

Accepted Answer

Water ($$H_2O)$$

Question 9

What is the formal charge on the nitrogen atom in the ammonium ion ($$NH_4$$^+$$)?

Accepted Answer

0

Question 10

Which of the following best explains why the bond angle in water ($$H_2O) is $$less than the bond angle in ammonia ($$NH_3$$)?

Accepted Answer

Water has two lone pairs on oxygen, which repel the bonding pairs more strongly than the single lone pair on nitrogen in ammonia.

Question 11

Which of the following is a correct statement about the electronegativity trend in the periodic table?

Accepted Answer

Electronegativity increases from left to right across a period and decreases down a group.

Question 12

Which of the following best describes the bonding in acetylene ($$C_2H_2$$)?

Accepted Answer

Each carbon is sp hybridized and forms a triple bond with the other carbon.

Question 13

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

Accepted Answer

Carbon dioxide ($$CO_2)$$

Question 14

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

Accepted Answer

$$	ext{Formal charge} = 	ext{Number of valence electrons} - (	ext{Number of unshared electrons} + \frac{1}{2} 	imes 	ext{Number of shared electrons})$$

Question 15

Which of the following best describes a dative (coordinate covalent) bond?

Accepted Answer

A bond in which both electrons are donated by one atom.

Question 16

Which of the following molecules has a trigonal planar geometry?

Accepted Answer

Ethylene ($$C_2H_4)$$

Question 17

Which of the following is a secondary amine?

Accepted Answer

Dimethylamine ($$CH_3NHCH_3)$$

Question 18

Which of the following best explains why the $$C=O$$ bond in a ketone is polar?

Accepted Answer

Oxygen is more electronegative than carbon, so the shared electrons are pulled closer to oxygen.

Question 19

Which of the following is the best resonance structure for the acetate ion ($$CH_3CO_2^-$$)?

Accepted Answer

Both resonance structures contribute equally because the negative charge is delocalized over two oxygen atoms.

Question 20

Which of the following statements about the octet rule is correct?

Accepted Answer

Second period elements cannot have more than eight electrons in their valence shell.

Covalent Bonding and Shapes of Molecules: Foundations of Organic Chemistry

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