Organic hydrogenation reactions, in which H2 and an "unsaturated" organic compound combine, are used in the food, fuel, and polymer industries. In the simplest case, ethene (C2H4) and H2 form ethane (C2H6). If 144 kJ is given off per mole of C2H4 reacting, how much heat is released when 14.6 kg of C2H6 forms?

Answer 1

Write the balanced chemical reaction:
C2H4 + H2 -> C2H6 , ΔH = -144 kJ/mol C2H4

Then we get the number of moles of C2H4 using the given mass, 14.6 kg of C2H6.
Molar mass, C2H6 = 2*12 + 6*1 = 30 g/mol
n,C2H6 = 14.6 * 1000 g / 30 g/mol = 486.67 mol
Since the mole ratio for C2H4 and C2H6 is 1:1,
n,C2H4 = 486.67 mol
Finally, we multiply the energy by this number of moles:
-144 kJ/mol C2H4 * 486.67 mol C2H4
= -70,080 kJ

Note that the negative sign just indicates that the heat is released.

Hope this helps~ :)