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