Answer: - 436.5 kJ.
Explanation:
According to Hess’s law of constant heat summation, the heat absorbed or evolved in a given chemical equation is the same whether the process occurs in one step or several steps.
According to this law, the chemical equation can be treated as ordinary algebraic expression and can be added or subtracted to yield the required equation.
The given chemical reaction is,
Now we have to determine the value of 
for the following reaction i.e,
According to the Hess’s law, if we divide the reaction by half then the will also get halved and on reversing the reaction , the sign of enthlapy changes.
So, the value 
for the reaction will be:
Hence, the value of for the reaction is -436.5 kJ.
For balancing acidic solutions, we would need to add H+ ions to the correct side of the equation to balance the total number of atoms and the overall charge.
Oxygen is 21% and nitrogen is 78% so combined is 99%
The diatomic molecule H2 has an extremely low boiling point because only weak Vander waals forces are present between the atoms of hydrogen molecule. This weak inter-molecular forces are easily broken when heat is apply resulting in low boiling point.
One electron is shared between ethane, H3-C-C-H3
