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

$$\text{Formal charge} = \text{number of valence electrons} - (\text{number of nonbonding electrons} + \frac{1}{2} \times \text{number of bonding electrons})$$

Question 1

Which of the following best explains why morphine can mimic the effects of endorphins in the human body?

Accepted Answer

Morphine has a similar molecular shape and functional groups as endorphins, allowing it to bind to the same biological receptors.

Question 2

Which of the following statements about electronegativity is correct?

Accepted Answer

Electronegativity increases from left to right across a period and decreases from top to bottom in a group.

Question 3

Given the following electronegativities: H (2.1), Cl (3.0), which type of bond is present in HCl?

Accepted Answer

Polar covalent bond

Question 4

Which of the following molecules violates the octet rule due to an incomplete octet?

Accepted Answer

BF$$_3$$

Question 5

What is the formal charge on the nitrogen atom in the ammonium ion (NH$$_4^+$$)?

Accepted Answer

$$0$$

Question 6

Which of the following best describes the geometry and bond angle of SF$$_6$$ according to VSEPR theory?

Accepted Answer

Octahedral, $$90^\circ$$

Question 7

A molecule has three bonding pairs and one lone pair on the central atom. What is its molecular geometry and approximate bond angle?

Accepted Answer

Trigonal pyramidal, $$\u003c109.5^\circ$$

Question 8

Which of the following molecules is expected to be nonpolar, despite having polar bonds?

Accepted Answer

CO$$_2$$

Question 9

Calculate the percent ionic character of a bond with a measured dipole moment of $$1.0 D $$and a bond length of $$127 pm. ($$Assume the charge separation is $$1.6 	imes 10$$^{-19}$$ C and 1$ D = 3.34$$ 	imes $$10^{-30} C$$·m.)

Accepted Answer

$$15\%$$

Question 10

Which of the following is a correct step in drawing the Lewis structure for the carbonate ion (CO$$_3$$^{2-}$$)?

Accepted Answer

Add two extra electrons to the total count to account for the $$2-$$ charge.

Question 11

Which of the following molecules or ions has an expanded octet?

Accepted Answer

SF$$_6$$

Question 12

Which of the following statements about resonance structures is correct?

Accepted Answer

Resonance structures have the same arrangement of atoms but different arrangements of electrons.

Question 13

Which of the following best describes the bond energy and bond length relationship?

Accepted Answer

As bond length increases, bond energy decreases.

Question 14

What is the molecular geometry of the nitrate ion (NO$$_3^-$$)?

Accepted Answer

Trigonal planar

Question 15

Which of the following molecules has a net dipole moment?

Accepted Answer

H$$_2O$$

Question 16

A molecule has five electron groups: three bonding pairs and two lone pairs. What is its molecular geometry?

Accepted Answer

T-shaped

Question 17

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

Accepted Answer

$$	ext{Formal charge} = 	ext{number of valence electrons} - (	ext{number of nonbonding electrons} + \frac{1}{2} 	imes 	ext{number of bonding electrons})$$

Question 18

Which of the following best explains why the bond angle in water (H$$_2O) is $$less than $$109.5^\circ$$?

Accepted Answer

Lone pairs on oxygen repel the bonding pairs more strongly, reducing the bond angle.

Question 19

Which of the following molecules is a free radical due to having an odd number of electrons?

Accepted Answer

NO

Chapter 5: Chemical Bonding I and Molecular Geometry

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