Question

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 140 kJ is given off per mole of C2H4 reacting, How much heat (in MJ) is released when 12 kg of C2H6 forms?

Answer 1

Answer: The amount of heat released is 56 MJ.

Explanation:

To calculate the number of moles, we use the equation:

$\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}$  

Given mass of $C_2H_6$ = 12 kg = 12000 g    (Conversion factor: 1 kg = 1000 g)

Molar mass of $C_2H_6$ = 30 g/mol

Putting values in above equation, we get:

$\text{Moles of }C_2H_6=\frac{12000g}{30g/mol}=400mol$

The chemical reaction for hydrogenation of ethene follows the equation:

$C_2H_4+H_2\rightarrow C_2H_6$

By Stoichiometry of the reaction:

When 1 mole of ethane releases 140 kJ of heat.

So, 400 moles of ethane will release = $\frac{140}{1}\times 400=56000kJ$ of heat.

Converting this into Mega joules, using the conversion factor:

1 MJ = 1000 kJ

So, $\Rightarrow 56000kJ\times (\frac{1MJ}{1000kJ})=56MJ$

Hence, the amount of heat released is 56 MJ.