USE THE dimensional analysis method to solve: In Brazil, vehicles are fueled almost entirely by ethanol C2H6O, which is produced from sugar cane. Calculate the heat (in kJ) produced by ethanol for each 2.50 kg of CO2produced.
first can sugar converts into glucose
C12H22O11 + H2O --------------> 2C6H12O6 ---------------->1
second glucose converts into ethanol and CO2
2C6H12O6 ------------------> 4C2H5OH + 4CO2 ---------------->2
overall reaction from 1 and 2
C12H22O11 (s) + H2O (l) ---------------> 4 C2H5OH (l) + 4CO2 (g)
H
=
Hproducts -
Hreactants
= (4 x –393.5 + 4 x –277.7)- (–285.8 –2226.1)
= -2684.8 + 2511.9
= -172.9 kJ /mol
4 CO2 is produced : 4 x 44 = 176 g
for 176 g CO2 -------------------> -172.9 kJ /mol
2.50 kg (2500 g) CO2 -------------> x kJ / mol
x = - 172.9 x 2500 / 176
x = -2456 kJ /mol
heat produced = - 2456 kJ /mol -----------------------------> answer
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