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Vol. 64
h70TES
Acknowledgment.-The
authors wish to thank
Dr. R. W. Stoughton for intcrcsting discussions in connection with this work.
nroirs
TABLE I11 HEATSOF SOIJJTION O F IiClO,,(e) IKX)~ x 103/
950
THERMOCHEMISTRY OF POTASSIUM PERMYANGANATE, POTASSIUM MOLYBDATE, POTASSIUM C,HLORATE, SODIlJM CHLORATE, SODIUM CHROMATE AND SODIUM DICHROMATE BYTHOMAS NELSON, CALVIN Moss AND LORENG. HEPLER~ Contribution from Cobb Chemirnl Lnborntorg. UniversifQ o f Virgiiiia Charluttuuille. Va. Received October 66,1969
1111.
A?l(kcnl./molr)
IT20
9.87 9.92 9.85 9.90 9.91 9.90
4.245 6.822 7 . 770 11.01
12.93 16.16
TABLE IV HEATSOF Sor.r~i,ro~ OF KaC103(c) Molrs NaCIO. X 102,' 9.50 nd. 1lzO
Al€(Rcnl./mole~
0.9260 1 ,032 1 .OF2 1,178 I .263 2.270
5.21 Heats of ,solut?ion of KMn04(c), KCIOa(c), 5.21 NaC103(c) and NnnCr04(c) and the heat of re5.23 action of Na26r207(c) with excess OH-(aq) have 5.23 been determimd as part of an undergraduate re5.24 search program. These heats have been used for 5.24 calculation of standard heats of formation of K2M004(c),Na2CrO4(c)and NazCrzOi(c)and standTABLE V ard partial rrtolal entropies of Mn04-(aq) and HEATSOF SOLUTION O F Nn2Cr04(c) IN l o w 3.If OH-(aq) ClOa-(aq).
Experimental The solution calorimeter used for these determinations has been described.*-* All calorimetric determinations were carried out at 25.0 f 0.2' with 050 ml. of water or solution in the calorimeter. All of the saltis were prepared for use in the calorimeter by recrystallization of the appropriate reagents and all except NaC1O8 and KCIO, were analyzed by common volumetric methods. Some samples were dried in vacuum desiccators and some in an air oven.
Rlolrs NaCrOd x lo'/ 950 nil. soln.
AH(konl./mole)
0,5632 ,6645 .979 1 1.016 1,137 1.408
-4.42 -4.44 -4.42 -4.3!) -4.43 -4.36
Heats of reaction of Nx2Crz07(c)with a small Results excess of aqueous NaOII as in the equation Heats of solution of KMn04(c), K2Mo04(c), Na2Cr207(c)+ 2OH-(aq) = 2Nn+(aq) + 2Cr04'(nq) + KC103(c), NaClOl(c) and Na2Cr04(c)are given in N20(1) ( 2 ) Tables I-V. I n each table, AH refcrs to the reare given in Table 1'1. action salt(c)
=
snlt(nq)
(1)
TABLE I HEATS OF SOLUTION O F
hloles IZMnOl X lo*/ 950 nil. HrO
4.810 5.G87 6. 345 6.5i0 7.187 9 !I I58
KMn04(c) A€l(kcal./molr)
10.42 10.30 10.43 10.44 10.42 10.44
TABLE I1 ~ I E A TOF~ SOLUTION OF K2MoOr(c) IN 10-8 A4 OH-(aq) Mole8 KrR'loOi X loz/ 950 nil. s d n .
0.5741 1.100
1.359 1 . ti23 1 ,746 I .784 2 . o"2
A??(kcnl./mole)
-0.82 - .79 - .82 - .79 - .75 - .i7 - .73
( 1 ) Alfred P. Sloan Foundation Research Fellow. ( 2 ) R. L. Gruhain and L. G . Ilepler, J . Ani. Chem. Sor., 7 8 . 48.16
(1956). ('0 N. RIiilrIrox, .Jr., and L. Q. Ilrpler, ihid. 79, 4045 (195;). ( 4 ) 3 f . R I R i r k y and L. C . llepier, to hr ~ ~ i ~ h l i s h e d .
(..
T A B L E VI HEATSO F SOLUTION O F K:&r207(r)
RTolrs NnrCrKh X 1 0 3 / 950 nll. s d n . AI(il?s 011- X IO2
2.087 2.646 4.302 4.640 5.106 6.549 6.567 8.566 10.482
1 .0 1.0 1.5 1.5 2.0 1.5 1.8 2 .5 2.5
IN
OH-(nq)
Alf(kcnl.,'~nole)
-21.36 -21 .:14 -21.33 -21.49 -21.36 -21.23 -21.32 -21.34 -21 26
Heats of dilution of I
