Based on the results of Exercise 71, which alkane evolves the greatest amount of heat upon combustion on 

(a) A per mole basis and 

(b) A per gram basis? Which is the most desirable alkane from the standpoint of reducing the emission of carbon dioxide to the atmosphere? Explain.

Exercise 71

Use data from Table 7.2 to calculate the standard enthalpies of combustion of the four alkane hydrocarbons listed there.

Table 7.2

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TABLE 7.2 Some Standard Molar Enthalpies of Formation, A+H° at 298.15 K Substance CO(g) CO₂(g) CH4(g) C₂H₂(g) C₂H4(g) C₂H6(g) C3H8(g) C4H10(g) CH₂OH(1) C₂H5OH (1) HF(g) HCl(g) kJ/mola -110.5 -393.5 -74.81 226.7 52.26 -84.68 -103.8 -125.6 -238.7 -277.7 -271.1 -92.31 Substance HBr(g) HI(g) H₂O(g) H₂O(1) H₂S(g) NH3(g) NO(g) N₂O(g) NO₂(g) N₂O4(g) SO₂(g) SO3(g) kJ/mola -36.40 26.48 -241.8 -285.8 -20.63 -46.11 90.25 82.05 33.18 9.16 -296.8 -395.7