NOTES Thermodynamic Functions for Phosphine and the Phosphonium Ion BY d U E I R E Y P. .\LTSHCLLEK RECEIVED JIARCH
23, 1955
TABLE I *
: 82 phosphine and gaseous phosphonium ion in the -400 11.98 9 . 09 1 2 ,$3,; tj2,0i temperature range from 200 to 1500" and 1000"K., .iOO 1:3 .;a 9 . 8;) 4 5 . (1.7 9f) respectively, by the rigid rotator-harmonic oscilla6!Kl 13.28 1o.lx -16.91 37 53 tor approximation for the ideal gas a t a pressure of 71x1 10 63 11.41 48.60 60.00 one atmosphere. The values of the thermodynamic Xf)O 17.81 1 2 . 1:3 50.17 62,BO functions are listed in Tables 1and 11. 900 12.83 18 83 ,51.64 64.47 At the lower temperatures the thermodynamic 1000 19.91 l a . -18 33 . 02 66.50 functions for phosphine should be uncertain to less than f0.1 cal. deg.,'inole. -kt temperatures near The uncertainties in the thermodynamic functions 1000°K. and above, neglect of anharmonicity and for PH4I due to the inaccuracies in the vibrational other effects can increase the uncertainties further. frequencies are difficult to estimate, but they probThe uncertainties in - ( F o - H,") 'T and S" for ably amount to several tenths of a cal./deg./mole. From low temperature heat capacity measurePH4+resulting from the uncertainty in its moment ~ ~entropy ~ ~ ~ of~ phosphine a t the b.p., of inertia amount to about =t 0.1 cal. 'deg./mole. m e n t the 1S5.3S°K., has been calculated to be 4G.39 =t 0.1 ( 1 ) D . 1'. Stevenson and L). .\I. Yost, J . C l i e n t . Phys., 9 , 103 (1CJll). cal. ,/deg./mole. The statistical thermodynaiiiic ( 2 ) H. hZ. Randall and S . \Vright, Phrs. Ru;. , 44, 3n1 (19:33). value for the entropy a t 1S3.3S"K. is 43.26 f 0.01 13) D. 11. Tost a n d T. F. hnder.;on, J . Cheiiz. P h y ? . , 2 , 6 2 4 (1931). (4) N. G . Pai, ~ l l d i n l tJ , P h y s . , 7 , 283 (IS332). cal. deg.!mole. The agreement is quite good, ( 5 ) Landolt-Btrnstein, "l'ahellen, S i x t h Edition, Molecules," Vu!. but the calorimetric value for S o does appear to be ringer-Verlag, Berlin 10.51, 2.i7. about 0.1 cal. /deg./mole too high. L . P r a t t a n d R . IC. Richards, 7'i.nns. F a v a d a y Soc., SO, 670 (1934). The previous statistical thermodynamic values' ( 7 ) IT. hf. AIcConaghrr a n d 15. H. Nielsen, Proc. S o f i . .4ciid. S,i ( r - , S . ) , 3 4 , 138 (1948). for -(F" - Ht)' T for PHa are 0.03 to 0.06 cal. (81 V. \l. >lcC'on:ighir ,itid I € 11. Nielsen, J . C h f m f ' l ! ? ~ , 21, 1831; deg. /mole higher in the temperature range from 29s ( 1 Lii:o. to 1500"I;.tliaii the values calculated iri this wurl;. f 9 ) 1) I,, s t r o u y , R . a (It1 I(.,, a n d E. 1:. Hell, J . o p t . soi...1 m . , 43, 'The previous statistical value' uf So for PHs at 1oY6 t l Y 5 3 J . (10) C C. 1,ournis a n d A i , \V P. Strandberg, P h y s . Rev., 81, 7YX 29S.16"K. is 0.03 cal./deg./mole too low. The val( 19.51). ues of So above 298°K. have not been given previI I I ) A 1 . 11 J i r v r t z a n d K. E. \Teston, J . Chem Phys., 21, 898 ( l Y 5 3 ) . ously. The entropy of the reaction I 111C . A B u r r u b , l r . , A Jache an,1 \V, (;only, P h y s . K m . , 9 5 , 7Oii ,
,
,
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,
O K .
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I
11
I
1 !J54).
(13) T h e moments of inertia given i n ref Y are I, = 7 . 2 3 X 1 0 - $0 : rm.? a n < I I ) , = I , = G 29 X l l ) - . i o c. ctn.2. T h e incredic is .So atill ~ - < / ? o - 11,:) 1' iiiiich V(,~II
