Q: Which formula is used to calculate the formal charge on an atom in a Lewis structure?

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

Q: Which equation is used to estimate the enthalpy change ($\Delta H$) of a reaction using bond energies?

$\Delta H = \sum \text{Bond energies of bonds broken} - \sum \text{Bond energies of bonds formed}$

Question 1

Which statement best explains why morphine is able to bind to pain receptors in the human body?

Accepted Answer

Morphine's molecular shape closely mimics the shape of endorphins, allowing it to fit into the receptor.

Question 2

Which of the following best describes a polar covalent bond?

Accepted Answer

A bond in which electrons are shared unequally due to a difference in electronegativity.

Question 3

Given the following electronegativities: $\mathrm{Cl} = 3.0$, $\mathrm{H} = 2.1$, $\mathrm{O} = 3.5$, which bond is expected to be the most polar?

Accepted Answer

$\mathrm{O-H}$

Question 4

Which formula is used to calculate the formal charge on an atom in a Lewis structure?

Accepted Answer

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

Question 5

Which molecule is an exception to the octet rule?

Accepted Answer

$\mathrm{BF_3}$

Question 6

What is the bond angle in a molecule with a trigonal planar electron geometry?

Accepted Answer

$120^\circ$

Question 7

Which of the following best describes the effect of lone pairs on molecular geometry?

Accepted Answer

Lone pairs decrease the bond angles between atoms due to increased electron repulsion.

Question 8

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

Accepted Answer

Trigonal pyramidal

Question 9

Which of the following molecules is expected to be nonpolar?

Accepted Answer

$\mathrm{CO_2}$

Question 10

Which equation is used to estimate the enthalpy change ($\Delta H$) of a reaction using bond energies?

Accepted Answer

$\Delta H = \sum 	ext{Bond energies of bonds broken} - \sum 	ext{Bond energies of bonds formed}$

Question 11

Which of the following best explains why oil and water do not mix?

Accepted Answer

Oil molecules are nonpolar and water molecules are polar, leading to immiscibility.

Question 12

Which of the following is the correct procedure for drawing a Lewis structure for a polyatomic ion?

Accepted Answer

Count the total number of valence electrons, add or subtract electrons for the charge, and distribute electrons to satisfy the octet rule.

Question 13

Which molecule has a net dipole moment?

Accepted Answer

$\mathrm{NH_3}$

Question 14

Which statement about resonance structures is correct?

Accepted Answer

Resonance structures represent different possible arrangements of electrons in a molecule, with the actual structure being a hybrid.

Question 15

Which of the following elements is most likely to form compounds with expanded octets?

Accepted Answer

$\mathrm{P}$

Question 16

A molecule has five electron groups around its central atom. What is its electron geometry?

Accepted Answer

Trigonal bipyramidal

Question 17

Which of the following best describes the relationship between bond length and bond strength?

Accepted Answer

Shorter bonds are generally stronger than longer bonds.

Question 18

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

Accepted Answer

$\mathrm{H_2O}$

Question 19

Which of the following is true about dipole moments?

Accepted Answer

Dipole moments arise from differences in electronegativity between atoms in a bond.

Question 20

Which VSEPR base shape corresponds to a molecule with six electron groups around the central atom?

Accepted Answer

Octahedral

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