Thermal Properties of Normal Chain Alkanes

Compounds in the Table in red (gases), blue (liquid) and solid (black) are at 25oC and 1 atmosphere pressure. ΔHo(c) are experimental heats of combustion (kcal/mol) under these conditions. From StdState is the heat liberated by an equivalent amount of graphite (ΔHfo(CO2) = -94.05 kcal/mol) and hydrogen (ΔHfo(l, H2O) = -68.3 kcal/mol) under the same conditions as the alkane. ΔHfo(l) is the heat of formation of the liquid (condensed phase), the difference between from StdState and ΔHfo(c). The difference between the heats of formation in the liquid (condensed) and gaseous phase is the heat of vaporization, ΔHfo(v). Estimated value.

The data reveal a regular increase per methylene group in the heat of combustion, a regular increase in the heat liberated from the Standard State and a regular increment in the heat of formation in the gaseous state. The missing data for C11, C13, C15, C17 and C19 are known but not entered in the Table. These values can be estimated by interpolation.

For a Table of Heats of Formation compared in the gas phase,
click here.
For Hess's Law of Constant Heat Summation,
click here.

 

Cmpd

#C

bp (oC)

mp (oC)

ΔHo(comb)

from StdState

ΔHfo(l)

ΔHfo (g)

ΔHo (v)

methane

1

-162

-183

-213

-231

-18

ethane

2

-89

-183

-373

-393

-20

propane

3

-42

-188

-531

-555

-24

butane

4

-0.5

-138

-687

-718

-31

pentane

5

-845

-880

-35

pentane

5

36

-130

-838

-880

-42

-35

7

hexane

6

69

-95

-995

-1042

-47

-40

7

heptane

7

98

-91

-1151

-1205

-54

-45

9

octane

8

126

-57

-1308

-1367

-59

-50

9

nonane

9

151

-54

-1464

-1529

-65

-55

10

decane

10

174

-30

-1620

-1692

-72

-60

12

undecane

11

196

-26

dodecane

12

216

-10

-1932

-2017

-85

-70

15

tridecane

13

235

-6

tetradecane

14

254

6

-2245

-2341

-96

-79

17

pentadecane

15

271

10

hexadecane

16

287

18

-2557

-2666

-109

-89

20

heptadecane

17

302

22

octadecane

18

316

28

-2870

-2991

-121

-99

22

nonadecane

19

330

32

eicosane

20

343

37

-3183

-3315

-133

-109

24