Question 1

The dipole moment of hydrogen chloride, HCl, is 1.08 D and the bond length is 127 pm. Calculate the fractional charge on the hydrogen and chlorine atoms. A) 8.50 *10^-3 C B) 2.84 * 10^-8 C C) 2.84 * 10^-20 C D) 2.84 *10^-20 C

Accepted Answer

The dipole moment (μ) is given by μ = q * d, where q is the charge and d is the bond length. Converting the dipole moment from Debye to Coulombs-meter and the bond length from pm to meters, we can solve for q.

Question 2

The Pauling electronegativities of chlorine and iodine are 3.0 and 2.5 respectively. Estimate the dipole moment of iodine monochloride, ICl.&#10;A) 0.0 D&#10;B) 0.5 D&#10;C) 2.5 D&#10;D) 3.0 D

Accepted Answer

The dipole moment is related to the difference in electronegativity between the two atoms. Since chlorine is more electronegative than iodine, ICl will have a dipole moment. The difference in electronegativity (3.0 - 2.5 = 0.5) suggests a dipole moment of approximately 0.5 D.

Question 3

The dipole moment of nitrobenzene is 3.99 D. Estimate the magnitude of the dipole moment in meta (1,3-)dinitrobenzene.&#10;A) 2.0 D&#10;B) 3.0 D&#10;C) 4.0 D&#10;D) 8.0 D

Accepted Answer

In meta-dinitrobenzene, the two nitro groups exert a dipole moment in opposite directions along the same axis. Since they are not directly opposite each other, they do not cancel out completely but are not additive either. The resultant dipole moment is less than the sum of the two individual moments but more than any one of them, making an estimate of around 4.0 D reasonable.

Question 4

The atomic coordinates and partial charges for the planar molecule fluoroethene, C₂H₃F, are
$\begin{array}{lrrrr} & x / A & y / A & z / A & \text { Partial charge } \\\mathrm{C} & -0.669 & 0.019 & 0.000 & +0.353 \mathrm{e} \\\mathrm{C} & 0.669 & -0.019 & 0.000 & -0.367 e \\\mathrm{H} & 1.211 & -0.978 & 0.000 & +0.039 \mathrm{e} \\\mathrm{H} & 1.265 & 0.906 & 0.000 & +0.041 e \\\mathrm{H} & -1.257 & -0.913 & 0.000 & 0.008 \mathrm{e} \\\mathrm{F} & -1.306 & 1.178 & 0.000 & -0.075 \mathrm{e}\end{array}$ Calculate the x and y components of the dipole moment.

A)

\mu

_x = -4.72 * 10^-30 C m,

\mu

_y = -1.33 *10^-30 C m
B)

\mu

_x = -0.295*10^-30 C m,

\mu

_y = -0.083 *10^-30 C m
C)

\mu

_x = -7.27 *10^-33 C m,

\mu

_y = -1.28 *10^-30 C m
D)

\mu

_x = 1.10 *10^-29 C m,

\mu

_y = 2.96*10^-30 C m

Accepted Answer

The dipole moment is a vector quantity that describes the separation of positive and negative charges in a molecule. The x-component of the dipole moment is given by the sum of the products of the partial charges and the x-coordinates of the atoms, and the y-component is given by the sum of the products of the partial charges and the y-coordinates of the atoms. In this case, the x-component of the dipole moment is:$$\mu_x = (0.353 	ext{ e})(0.669 	ext{ Å}) + (-0.367 	ext{ e})(-0.669 	ext{ Å}) + (0.039 	ext{ e})(1.211 	ext{ Å}) + (0.041 	ext{ e})(1.265 	ext{ Å}) + (0.008 	ext{ e})(-1.257 	ext{ Å}) + (-0.075 	ext{ e})(-1.306 	ext{ Å}) = -4.72 	imes 10^{-30} 	ext{ C m}$$and the y-component is:$$\mu_y = (0.353 	ext{ e})(0.019 	ext{ Å}) + (-0.367 	ext{ e})(-0.019 	ext{ Å}) + (0.039 	ext{ e})(-0.978 	ext{ Å}) + (0.041 	ext{ e})(0.906 	ext{ Å}) + (0.008 	ext{ e})(-0.913 	ext{ Å}) + (-0.075 	ext{ e})(1.178 	ext{ Å}) = -1.33 	imes 10^{-30} 	ext{ C m}$$

Question 5

The dipole moment of an ozone molecule, O₃, is 0.53 D. The molecule has a symmetrical bent structure so that, if the molecule is assumed to lie in the yz plane, the terminal atoms have coordinates ( $\pm$ 0.678 Å,0,-0.362 Å) and the central atom has coordinates (0,0,0.724 Å). The terminal atoms have a net negative partial charge and the central atom has a net positive partial charge. Determine the magnitude of the partial charges on each of the oxygen atoms.

A) Terminal: -0.051e Central: +0.102e
B) Terminal: -0.076e Central: +0.076e
C) Terminal: -0.102e Central: +0.102e
D) Terminal: -0.108e Central: +0.215e

Accepted Answer

The dipole moment ($\mu$) of a molecule can be calculated using the formula $\mu = q \times d$, where $q$ is the magnitude of the charge and $d$ is the distance between the charges. Given that the dipole moment of ozone is 0.53 D and the structure is symmetrical, we can deduce that the charges on the terminal atoms are equal in magnitude but opposite in sign to the charge on the central atom. The distance between the charges can be calculated based on the given coordinates, which leads to the conclusion that the charges must balance out to give the correct dipole moment. Option A provides a set of charges that, when multiplied by the appropriate distances, would result in the given dipole moment, considering the symmetry and geometry of the molecule.

Question 6

Determine the strength of the electric field necessary to induce a dipole moment of1.0 $\mu$D in sulfur hexafluoride, SF₆, which has been calculated to have a polarizability volume of 4.00 Å³. A) 1.7 kV m^-1 B) 6.2 kV m^-1 C) 95 kV m^-1 D) 7.5 kV m^-1

Accepted Answer

The answer of Determine the strength of the electric field...

Question 7

Calculate the magnitude of the potential energy for the interaction of two co-linear hydrogen fluoride, HF, molecules whose centres are separated by 5.0 Å. The dipole moment of a hydrogen fluoride molecules is 1.91 D.

A) 1.9 * 10^-21 J
B) 12 *10^-22 J
C) 5.8 * 10^-21 J
D) 2.9 * 10^-21 J

Accepted Answer

The answer of Calculate the magnitude of the potential energy...

Question 8

Estimate the potential energy resulting from the dispersion interaction between two xenon, Xe, atoms at a separation of 4.80 Å. The polarizability volume of a xenon atom is 4.16 Å³ and the ionization energy is 12.1 eV.

A) -1.26* 10^-22 J
B) -5.71 *10^-3 J
C) -3.50 * 10^-22 J
D) -9.14 * 10^-22 J

Accepted Answer

The answer of Estimate the potential energy resulting from the...

Question 9

The mean separation between chlorine, Cl₂, molecules, at a temperature of 298.15 K and a pressure of 1 bar is 3.5 nm. Given the values of the Lennard-Jones parameters are $\varepsilon$ = 368 kJ mol^-1 and r ₀ = 412 pm, use the Lennard-Jones function to calculate the potential energy between pairs of xenon atoms at this separation.

A) -3.9 J mol^-1
B) 0.0 J mol^-1
C) -0.98 J mol^-1
D) -15 J mol^-1

Accepted Answer

The answer of The mean separation between chlorine, Cl₂, molecules,...

Question 10

The Lennard-Jones parameters for the interactions between benzene, C₆H₆, molecules are $\varepsilon$ = 454 kJ mol^-1 and r₀ = 527 pm. Calculate the separation that corresponds to the minimum in the Lennard-Jones potential.

A) 592 pm
B) 527 pm
C) 1054 pm
D) 745 pm

Accepted Answer

The separation that corresponds to the minimum in the Lennard-Jones potential is given by $r_{min} = 2^{1/6} \times \sigma$, where $\sigma$ is the distance at which the potential energy is zero. Given $\sigma = 527$ pm, $r_{min} = 2^{1/6} \times 527$ pm ≈ 592 pm.

Deck 10: Molecular Interactions