Question

Calorific value of ethane in kj/g if for the reaction

Answer 1

Hey dear,
You didn't mention the reaction.

● Complete question -
Calorific value of ethane, in kJ/g if for the rxn 2C2H6 + 7O2--- 4CO2 + 6H2O ∆H = +746 kcal

● Answer -
Calorific value = -52.22 kJ/g

● Explanation -
In the reaction, 2 ethane molecules are burnt, so heat of combustion is -
∆Hc = -746/2 kcal/mol
∆Hc = -373 kcal/mol
∆Hc = -373×4.2 kJ/mol
∆Hc = -1566 kJ/mol

Calorific value is calculated by -
Calorific value = heat of combustion / molar mass
Calorific value = -1566/30
Calorific value = 52.22 kJ/g

Therefore, calorific value of ethane is 52.22 kJ/g.




* Most imp - keep track on units here.

Hope this helps you...

Answer 2

from the given data heat of combustion of ethane will be =-745.6 / 2 = -372.8 K cal mol-1

1K cal = 4.18J

∴-372.8 K cal = 372.8 x 4.18 =1559.7959 KJ/mol

Calorific value = heat of combustion/ gram moleculat wt. of fuel = 1559.8 / 30 = 52 KJ /g