Thermodynamic Behavior of Tetraalkylammonium Bromide and

17 Thermodynamic Behavior of Tetraalkylammonium Bromide and Hydrobromic Acid in Aqueous Media at

Downloaded by FUDAN UNIV on March 11, 2017 | http://pubs.acs.org Publication Date: June 1, 1979 | doi: 10.1021/ba-1979-0177.ch017

298.15 Κ R. N. ROY, J. J. GIBBONS, J. MOELLER, and R. SNELLING Department of Chemistry, Drury College, Springfield, MO 65802

Electromotive force measurements of the cell (without liquid junction) of the type Pt; H (g, 1 atm)|HBr(m ), (C H ) NBr(m )|AgBr; Ag have been made at several constant total molalities (m = 0.05, 0.1, 0.25, 0.5, 1.0, and 1.5 mol-kg , where m = m + m ), at 298.15 K. The trace activity coeffi cients of HBr in HBr + (C H ) NBr + H O mixtures, the Harned interaction coefficients (α and α ), the BronstedGuggenheim parameter (β(C H )4N+,Βr-), the Pitzer param etersΘMN(cation-cation doublet interaction), and Ψ (cation-anion-cation triplet interaction), along with the excess Gibbs free energies of mixing,ΔG ,at 298.15 K, are reported. Interpretation of these results has been made in light of recent work by Pitzer. The results are discussed also in relation to the structural changes of water caused by the presence of the large-sized hydrophobic cation [(C H ) N ]. 2

1

2

5

4

2

-1

1

2

2

5

4

2

12

2

21

5

MNX

E

+

2

5

4

n p h e d e t e r m i n a t i o n o f t h e a c t i v i t y coefficient o f a n e l e c t r o l y t e i n b i n a r y Α

m i x t u r e s o f a n o t h e r e l e c t r o l y t e w i t h a c o m m o n i o n has p r o m p t e d

c o n s i d e r a b l e interest, b o t h i n t h e d e v e l o p m e n t o f t h e u n d e r l y i n g t h e o r y , as w e l l as p r e c i s e e x p e r i m e n t a l measurements.

T h i s k i n d o f s t u d y is u s e f u l

i n a p p l i c a t i o n s t h a t i n v o l v e m e t a l l u r g i c a l a n d b i o l o g i c a l systems. interaction parameters (doublet a n d triplet, among others)

The ion

responsible

f o r a n u n d e r s t a n d i n g o f t h e effects o f c a t i o n size o n t h e t h e r m o d y n a m i c 0-8412-0428-4/79/33-177-263$05.00/l © 1979 American Chemical Society

Furter; Thermodynamic Behavior of Electrolytes in Mixed Solvents—II Advances in Chemistry; American Chemical Society: Washington, DC, 1979.

264

THERMODYNAMIC BEHAVIOR OF ELECTROLYTES H

b e h a v i o r of t e t r a a l k y l a m m o n i u m s a l t - w a t e r m i x t u r e s a r e w e l l r e c o g n i z e d T h e r e has b e e n some progress t o w a r d s u n r a v e l l i n g t h e c o m p l e x

(1-12).

n a t u r e of these i n t e r a c t i o n s , b u t the results are s t i l l f a r f r o m q u a n t i t a t i v e . A s a c o n t i n u a t i o n of o u r p r e v i o u s investigations to s t u d y t h e t h e r m o d y n a m i c b e h a v i o r of m i x t u r e s of s t r o n g aqueous electrolytes, s u c h as H C l + NH4CI + H 0 ( 13), H B r +

NH Br +

2

+

H 0 (25), H B r +

H 0 2

+

2

5

9

4

HBr+

2

H 0 (16), 2

(C H ) NBr

and H C l +

3

7

4

LaCl

+

3

w e h a v e m a d e e l e c t r o m o t i v e f o r c e measurements o n the H B r

(17),

(C H ) NBr +

m =

4

H 0 (14),

4

(C H ) NBr +

2

4

H 0 system at 298.15 Κ i n t h e t o t a l m o l a l i t y r a n g e 2

0.05-1.5 m o l - k g " . T h e d a t a for t h e a c t i v i t y a n d o s m o t i c 1

of p u r e ( C H ) N B r are a v a i l a b l e i n the l i t e r a t u r e (9,10), 2

5

coefficients

based on either

4


e m f or g r a v i m e t r i c i s o p i e s t i c v a p o r pressure t e c h n i q u e s , b u t no t h e r m o d y n a m i c d a t a for v a r i o u s m i x t u r e s of t h e H B r +

(C H ) NBr -f

H 0

system h a v e b e e n r e p o r t e d i n the l i t e r a t u r e . E m f measurements

were

2

5

4

2

m a d e therefore at 298.15 Κ u s i n g a c e l l of the t y p e ( w i t h o u t transference):

P t ; H ( g , 1 a t m ) l H B r ( m ) , ( C H ) N B r ( m ) |AgBr, A g 2

Experimental

1

2

5

4

(1)

2

Procedure

T h e hydrobromic acid used was twice-distilled, constant-boiling acid. T r i p l i c a t e g r a v i m e t r i c analyses of the stock s o l u t i o n o f a q u e o u s H B r ( a b o u t 3 M ) a g r e e d to w i t h i n ± 0 . 0 1 % . T h e t e t r a e t h y l a m m o n i u m b r o m i d e ( E a s t m a n K o d a k Co.) was recrystallized twice from benzene-ligroin m i x t u r e s , as r e c o m m e n d e d b y U n n i et a l . (18). T h e m o l a l i t y of t h e stock s o l u t i o n ( a b o u t 4 M ) w a s s t a n d a r d i z e d b y g r a v i m e t r i c d e t e r m i n a t i o n of b r o m i d e a n d w a s a c c u r a t e to w i t h i n =b 0 . 0 2 % . E m f measurements w e r e m a d e w i t h a L e e d s a n d N o r t h r u p K - 5 p o t e n t i o m e t e r e q u i p p e d w i t h a L e e d s a n d N o r t h r u p D C n u l l detector ( M o d e l 9 8 2 9 ) . T h e t e m p e r a t u r e of the b a t h w a s r e g u l a t e d to w i t h i n 0.02 K . D e t a i l s of the e x p e r i m e n t a l p r o c e d u r e , i n c l u d i n g p r e p a r a t i o n of the electrodes (19), c e l l d e s i g n , p r e p a r a t i o n of solutions, p u r i f i c a t i o n of the h y d r o g e n gas, a n d other e x p e r i m e n t a l aspects, h a v e b e e n r e p o r t e d elsewhere (13,14). P r e l i m i n a r y e m f measurements w e r e m a d e o n C e l l I , a n d t h e s t a n d a r d p o t e n t i a l of the A g - A g B r electrode w a s d e t e r m i n e d as 0.07106 V f r o m d a t a t a k e n i n 0.01000 m o l k g " h y d r o b r o m i c a c i d . T h i s v a l u e of E ° w a s i d e n t i c a l w i t h that g i v e n i n the l i t e r a t u r e (20). T h e emf v a l u e s w e r e r e p r o d u c i b l e u p to m = 1.0 m o l k g " . T h e r e w a s some e v i d e n c e of i r r e v e r s i b l e b e h a v i o r for m = 1.5 m o l k g " . I n o r d e r to a v o i d this k i n d of d r i f t i n the e m f values at t h e highest constant t o t a l m o l a l i t y tested, t h e c e l l w i t h the h y d r o g e n electrode w a s a l l o w e d to e q u i l i b r a t e f o r ~ 45 m i n b e f o r e the A g - A g B r electrode ( w h i c h w a s k e p t i n a separate s t a n d a r d j o i n t test t u b e c o n t a i n i n g a s o l u t i o n of the same c o m p o s i t i o n ) w a s t r a n s f e r r e d to the electrode c o m p a r t m e n t . T h e e q u i l i b r i u m emf v a l u e w a s r e c o r d e d every 5 m i n u n t i l n o d e v i a t i o n w a s n o t i c e d . 1

m

1

1


17.

Tetraalkylammonium

ROY ET AL.

265

Bromide

Table I . Experimental E m f D a t a of the Cell P t ; H (g, 1 a t m ) | H B r ( ) , ( Q > H ) N B r ( m ) j A g B r ; A g at 2 5 ° C , in Volts, for Various Values of a Obtained from Equation 6 2

W l

5

2

4

12

m = 0.05 mol kg' m = 0.1 mol kg' m = 0.25 mol kg' m ~ 0.5 mol kg' 1

E,V

Ύ2

Ύ2

0 0.24592 0.47618 0.63776 0.75506 0.86248

0 0.24300 0.49490 0.65570 0.75210 0.87430

m = 1.0 mol kg'

1

«12

=

=

0 0.10650 0.25920 0.46970 0.67370 0.87920

012

0.0007 0.07765 0.08125 0.08602 0.09206 0.09624 0.09996

— 0.3044 = 0.0007 • -0.1021 =• = 0.0008 = 0.00007

0 0.10650 0.25920 0.46970 0.67370 0.87920

0.00023

0 0.23548 0.49526 0.63534 0.73706 0.86290

0.15512 0.15837 0.16613 0.17670 0.19063 0.21673

0.11837 0.12901 0.14365 0.15397 0.16400 0.18264

m = 1.5 mol kg'

1

E,V

«12

σ{βα) σ(Ε)

=

σ(Ε) = 0.00007

1

a i 2

σ(«ΐ2)

0.0015

2

σ(Ε)

y*

σ(αΐ2)

m = 1.5 mol kg'

1

0.2156

σ(N\ (Et)N+) are n e g l i g i b l y s m a l l , b u t Φ +, ΒΓ-, (Et)N+ is o f c o n 4

4

Η

4

siderable importance at higher concentrations. Table III.

4

Frank and Evans (29),

Comparison of the Values of the Pitzer Interaction

Parameters Θ and Ψ for H C l + HBr

NH Cl, HBr+

-f- Various Substituted

4

N H ^ B r , and

Tetraalkylammonium

Bromides i n Water at 2 5 ° C System HC1 HBr HBr HBr HBr

+ NH C1 + H + NH Br + H + (C H ) NBr + (C H ) NBr + (C H ) NBr 4

4

2

5

4

3

7

4

4

9

4

Θ 0 O + H O + H O + H 0' &

2

2

e

2

2

2

d

e

3.0

3.0 1.5 2.0 1.0

-0.016 -0.019 -0.20 -0.17 -0.22

5

5

0.0 (assumed) 0.0 (assumed) -0.19 -0.15 0.0 (assumed)

Maximum molality studied. Ref. 13. Ref. 14. Present investigation. " Ref. 16. Ref. 16. 0

6

e

d

1


274

T H E R M O D Y N A M I C BEHAVIOR O F E L E C T R O L Y T E S

II

R a s a i a h ( 3 0 ) , a n d W o o d a n d A n d e r s o n ( 3 1 ) h a v e s t u d i e d t h e effects o f large-sized tetraalkyl h y d r o p h o b i c cations o n m i x e d strong electrolyte systems.

T h e i r observations s h o w t h a t this k i n d o f salt tightens t h e

s t r u c t u r e o f w a t e r a r o u n d t h e m i n a w a y s i m i l a r t o some a l i p h a t i c h y d r o carbons. H e n c e , t h e s t r u c t u r a l effect ( o r e n t r o p y effect) o f ( E t ) N 4

comparison w i t h N H

+ 4

+

in B

w i l l b e large. T h e m o r e n e g a t i v e v a l u e s o f AG +

w o u l d suggest t h e f o r m a t i o n o f m o r e H ( E t ) N 4

+

pairs than w o u l d be

e x p e c t e d f r o m statistical encounters. S i m i l a r studies o n H B r + t r i e t h y l a m m o n i u m b r o m i d e ( a surfactant)

N-decyl-

a r e a t p r e s e n t i n progress t o

gain more insight into the nature of complex interactions o f m i x e d aqueous


e l e c t r o l y t e solutions ( 3 2 ) .

Acknowledgment The

authors are g r a t e f u l t o T . W h i t e , w h o p e r f o r m e d s o m e o f t h e

p r e l i m i n a r y measurements,

a n d t o the C o m p u t e r C e n t e r at S o u t h w e s t

M i s s o u r i State U n i v e r s i t y i n S p r i n g f i e l d , o n w h o s e I B M 360 t h e c a l c u l a tions w e r e d o n e . A c k n o w l e d g m e n t is m a d e to t h e D o n o r s o f t h e P e t r o leum Research F u n d

( G r a n t 9725-B5), administered b y the A m e r i c a n

C h e m i c a l S o c i e t y , f o r c o m p l e t e s u p p o r t o f this research.

Literature Cited 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19.

Pitzer, K. S.,J.Phys. Chem. (1973) 77, 268. Pitzer, K. S., Mayorga, G., J. Solution Chem. (1974) 3, 539. Pitzer, K. S., Mayorga, G., J. Phys. Chem. (1973) 77, 2300. Pitzer, K. S., Kim, J. J., J. Am. Chem. Soc. (1974) 96, 5701. Silvester, L. F., Pitzer, K. S., J. Solution Chem., submitted for publication. Kessler, Y. M., Grouba, V. D., Kiryanov, V. Α., Yemelin, V. P.,J.Solution Chem. (1977) 6, 231. Boyd, G. E., J. Solution Chem. (1977) 6, 135. Harned, H . S., Robinson, R. A., "Multicomponent Electrolyte Solutions," Pergamon, Oxford, 1968. Lindenbaum, S., Boyd, G. E., J. Phys. Chem. (1964) 64, 911. Wen, W., Miyajima, K., Otsuka, Α.,J.Phys. Chem. (1971) 75, 2148. Ramanathan, P. S., Krishnan, C. V., Friedman, H . L., J. Solution Chem. (1972) 1, 237. Leyendekkers, J. V., Hunter, R. J., J. Electroanal. Chem. (1977) 81, 123. Robinson, R. Α., Roy, R. N., Bates, R. G.,J.Solution Chem. (1974) 3, 837. Roy, R. N., Swensson, E., J. Solution Chem. (1975) 4, 431. Roy, R. N., Gibbons, J. J., Snelling, R., Moeller, J., White, T.,J.Phys. Chem. (1977) 81, 391. Roy, R. N., Gibbons, J. J., Krueger, C., White, T., J. Chem. Soc., Faraday Trans. I (1976) 72, 2197. Roy, R. N., Gibbons, J. J., Buechter, K., Faszholz, S., J. Solution Chem., to be submitted soon. Unni, A. K. R., Elias, L., Schiff, H. I.,J.Phys. Chem. (1963) 67, 1216. Bates, R. G., "Determination of pH," 2nd ed., pp. 283, 331, Wiley, New York, 1973.


17.

ROY ET AL.

Tetraalkylammonium Bromide

275


20. Hetzer, Η. Β., Robinson, R. Α., Bates, R. G., J. Phys. Chem. (1962) 66, 1423. 21. Lewis, G. N., Randall, M., "Thermodynamics," rev. by Κ. S. Pitzer, L . Brewer, Chap. 23, McGraw-Hill, New York, 1961. 22. Guggenheim, Ε. Α., Turgeon, J. C., Trans. Faraday Soc. (1955) 51, 747. 23. Scatchard, G.,J.Am. Chem. Soc. (1961) 83, 2636. 24. McKay, H. A. C., Trans. Faraday Soc. (1955) 51, 903. 25. Mayer, J. E.,J.Chem. Phys. (1950) 18, 1426. 26. Friedman, H. L., "Ionic Solution Theory," Wiley, New York, 1962. 27. Pitzer, K. S.,J.Phys. Chem. (1974) 78, 2698. 28. Pitzer, K. S.,J.Solution Chem. (1975) 4, 249. 29. Frank, H. S., Evans, M. W.,J.Phys. Chem. (1945) 13, 507. 30. Rasaiah, J. C.,J.Chem. Phys. (1970) 52, 704. 31. Wood, R. H., Anderson, H. L.,J.Phys. Chem. (1967) 71, 1871. 32. Pitzer, K. S., Roy, R. N., Silvester, L. F., J. Am. Chem. Soc. (1977) 99, 4930. RECEIVED March 10, 1978.


Thermodynamic Behavior of Tetraalkylammonium Bromide and

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