Lab 6 Report Dipole Moment PDF

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Lab 6 Report Dipole Moment...

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Hieu Pham CHEM 4081 – Physical Chemistry II Lab 6 Report: Measurement of Dipole Moment February 28th, 2021

Abstract: The main objective for this experiment is to calculate dipole moments of two compounds, odichlorobenzene (o-DCB) and m-dichlorobenzene (m-DCB) by measuring the closed and open capacitances of the capacitor dipped in the solutions with different concentration of each compound. Using two method of GNS, the calculated dipole moments of o-DCB were found to be 2.66 D and 1.477 D, and those of m-DCB were found to be 2.279 D and 0.999 D. From the experiment, the dipole moments calculated from the data were 1.43 D for o-DCB and 0.344 for m-DCB. After looking for the literature value of chlorobenzene1, which is 1.63 D, the dipole moments of o-DCB and m-DCB were found to be 2.66 D and 1.63 D, respectively. It can be concluded that using the first method of GNS gave the exact value of dipole moment compared to the literature value but not the second method. However, the dipole moments calculated for mDCB for both GNS methods and for both o-DCB and m-DCB from the experiment were not close to the literature values, this can be explained by mistakes while doing the math/ calculations and wrong collected data while performing the experiment.

Experimental: The experiment was performed and followed exactly as instructed in the Measurement of Dipole Moment Lab Handout2 by Dr. Colquhoun. Furthermore, the calculations were obtained from the lab handout and Experiment 313 (5th Ed, posted on Canvas). While doing the experiment, we had a mistake that we did not fully open the capacitance therefore we had to re-do the experiment for each of the concentration of solution and got new value of open capacitance. Otherwise, all the steps were followed strictly and exactly as instructed. Data and Results: A)

o-DCB concentratio n (mol/mL)

open cap (nF)

close d cap (nF)

open cap air (nF)

9.40*10-5

0.145

0.82

0.266

1.860*10-4 2.761*10-4 3.690*10-4 4.60*10-4

0.134 0.137 0.13 0.154

0.836 0.858 0.851 0.866

close d cap air (nF) 0.425

 sample (dielectri c constant) 4.245

Infractiv e index (n)

LHS

Pu

(dipole momen (D)

1.423

0.265

41.75 7

1.43

4.415 4.534 4.534 4.478

1.424 1.426 1.426 1.428

0.277 0.285 0.285 0.280

Table 1. experimental o-DCB values

Figure 1. o-DCB concentration vs LHS eqn 10

m-DCB concentratio

open cap

closed cap

Infractive index (n)

 sampl

LHS

P

 (D)

open cap

closed cap air

Densit y

n (mol/mL) 0.00132

(nF)

(nF)

0.12

0.813

0.00232

0.129

0.00310

0.133

0.00372

0.14

0.00423

0.136

e 1.4263

2.056

0.0040 2.423 4 0.824 1.4265 2.063 0.0050 1 0.828 1.4276 2.062 0.0044 3 0.841 1.4299 2.080 0.0064 5 0.85 1.4307 2.118 0.0129 Table 2. experimental m-DCB values

Figure 2. m-DCB concentration vs LHS eqn 10.

0.344

air (nF) 0.102

(nF)

(g/mL)

0.439

0.821 0.826 0.827 0.832 0.843

B)

Figure 3.  vs. mole fraction o-DCB

Figure 4. o-DCB density vs. mole fraction

Figure 5. o-DCB n2 vs. mole fraction

Densit y of oDCB in pure state (g/mL) 1.306

1 2

a

b

P02d (m3/m ol)

P02m (m3/m ol)

5.8491

0.379

28.82* 10-6

1.166* 1.454*104 10-4

8.88*10-30 Cm 4.93*10-30 Cm

P02(1) (m3/mol)

c

n12

P02(2) (m3/mol)

1

ρ1

0.262 3

2.024 1

4.468*10-

4.26 6

0.801 9

2.66 D 1.477D

Table 3. o-DCB GNS Method values

5

Figure 6. m-DCB dielectric constant vs mole fraction

Figure 7. m-DCB density vs mole fraction

Figure 8. m-DCB n2 vs mole fraction

Densit y mDCB in pure state (g/mL) 1.29

1 2

a

b

P02d (m3.m ol-1)

P02m (m3.m ol-1)

P02 (m3.mo l-1)

c

n1 2

P02(2) (m3.mol1 )

1

ρ1

1.4243

0.5

2.910* 10-5

7.737 *10-5

1.064* 10-4

0.34 85

2.029 3

20.48

2.033 2

0.814 8

7.603*10-30 Cm 3.336*10-30 Cm

2.279 D 0.999 D

Table 4. m-DCB GNS method values

C) Simulation Experimental dipole moment of CB was found to be 1.63 D CB (D) 1.63

o-DCB (D) 2.8

m-DCB (D) 1.63

Calculated values of dipole moments of o-DCB were 2.66 D and 1.477 D, for m-DCB were 2.279 D and 0.099 D.

Calculations: A) o-DCB concentration: Mo-DCB = mol DCB/ volume solution = 0.019(mol)/(200+2.14) (mL) = 9.40*10-5 mol/mL Dielectric constant: sample = (Cclosed – Copen)solution / (Cclosed – Copen)air = (0.82 – 0.145)/( 0.425 – 0.266) = 4.245 LHS of equation 10: LHS = (-1)/( +2) – (n2 -1)/(n2+2) = (4.245-1)/(4.245+2) – (1.4232 – 1)/(1.4232 +2) = 0.265 Dipole moment:  = 0.01281*(PT)0.5 = 0.01281* (0.3822*298(K))0.5 = 0.137 D B) Method 1: P02d (o-DCB) = (n22 – M2)/(n22 + 2* ρ2) = (1.5512 – 147.01(g/mol))/(1.5512 + 2*1.306(g/mL)) = -28.82 mL/mol * 10-6 (m3/mL) = -2.882*10-5 m3/mol P2m0 (o-DCB) = (3*M1*a)/(( 1 + 2)2* ρ1) + ((1 -1)/(( 1 + 2)* ρ1))*(M2 – M1*b/ ρ1) = 3* 84.16(g/mol)*5.8491/((4.266+2)2*0.8019(g/mL)) + ((4.266-1)/ (4.266+2)*0.8019))*(147.01(g/mol) – 84.16(g/mol)*0.379/0.819(g/mL)) * 10-6 (m3/mL) = 1.166*10-4 m3/mol P2u0 (1) = P2m0 – P2d0 = 1.166*10-4 - -2.882*10-5 m3.mol = 1.454*10-4 m3/mol Dipole moment 1 = 42.7*( P2u0 (1)*298(K))0.5*10-30 C m = 8.88*10-30 C m = 12.8*(*( P2u0 (1)*T)0.5 = 2.66 D Method 2:

P2u0 (2) = (3*M1/ ρ1)*((a/( 1 + 2)2 - c/(n12 +2)2) = (3*84.16 (g/mol)/0.8019 (g/mL)) *(5.8491/(4.266+2)2 – 0.2623/(2.0241 + 2)2) *10-6 (m3/mL) = 4.468*10-5 m3/mol

2 = 42.7*( P2u0 (2)*298(K))0.5*10-30 C m = 4.93*10-30 C m = 12.8*(*( P2u0 (2)*298(K))0.5 = 1.477 D C) Simulations: o-DCB = (CB 2 + CB 2 + 2*CB *CB *cos(60))0.5 = 2.66 D m-DCB = (CB 2 + CB 2 + 2*CB *CB *cos(120))0.5 = 1.63 D

Discussion/Conclusion:

Using two method of GNS, the calculated dipole moments of o-DCB were found to be 2.66 D and 1.477 D, and those of m-DCB were found to be 2.279 D and 0.999 D . From the experimental data, the dipole moments calculated from the data were 1.43 D for o-DCB and 0.344 for m-DCB. After looking for the literature value of chlorobenzene1, which is 1.63 D, the dipole moments of o-DCB and m-DCB were found to be 2.66 D and 1.63 D, respectively. We can see that there was only the value of o-DCB of first GNS method was the same value with its literature value, but the rest of the dipole moments value, including m-DCB, were not even close to the literature ones. This can be explained by the mistakes while working on the calculations therefore giving the wrong results, or mistakes while performing the experiment then wrong experimental data was collected. To make the experimental and theoretical dipole moment values to be closer to the literature values, it is recommended to do the calculations more carefully and take care of the units of each variable in the calculations, and also do the experiment more carefully as well.

Reference. 1.

Sharma, V. , Thakur, N. Dielectric Relaxation Studies of Binary Mixtures of Ethanol and Chlorobenzene in Benzene Solution from Microwave Absorption Data. Zeitschrift fur Naturforschung ,2008, a. 63. 93. 10.1515/zna-2008-1-21 2

Colquhoun, C. “Measurement of Dipole Moment”. Auburn University, 2021.

3

Guggenheim, E.A, “A proposed Simplification in the Procedure for Computing Electric Dipole Moments”, Trans. Faraday Soc., 45,714-720, 1949. Atkins, P.W, “Physical Chemistry”, Oxford: Oxford University Press, 11th ed, 2018....