Calculate the heat of combustion of 1.00 g of each alcohol considering the heat they released after a combustion experiment: Methanol: -22.6 kJ; ethanol: -29.7 kJ; n-propanol: -33.4 kJ. What can you notice from the data?

 

eat of combustion:

methanol (CH₃OH)= -7.23 x 102 kJ/mol = -723 kJ/mol

ethanol(C₂H₅OH) = -1.37 x 103 kJ/mol = -1370 kJ/mol

n-propanol(C₃H₇OH) = -2.00 x 103 kJ/mol = -2000 kJ/mol

Based from the data, the heat of combustion increases in magnitude as the number of carbons increases (|?ΔHmethanol??| < |?ΔHethanol??| < |?ΔHn−propanol??|). The reason why heat of combustion increases as the number of carbons increases is there are more carbons available for combustion present in the molecule.

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