[biomed77]

calculate the heat produced per gram of each fuel in the above table, that is the specific enthalpy/kj g-1 (atomic masses: C=12, O=16, H=1)

Right the table has as follows: CH4 = -890.3  H2=-285.8  C8H18 = -5470.2  These are the standard enthalpy of combustion/kj mol-1

answer: CH4= 12+4*1=16g. =1 mol of CH4= -55.64kj g-1
H2= 1+1=2g. = 1 mol of H2 so -285.8 / 2 = -142.9 kj g-1
C8H18 = 12*8+18*1=114g.= 1 mol of C8H18 so -5470.2/114= -47.98 kj g-1
then it asks which is the best fuel from the point of view of specific enthalpy and i say H2...am i right? if no, can someone please correct me? many thanks...

[xiankai]

yes you are right. hydrogen gas is one of the most efficient fuels known to mankind.