Explanation:
As per the 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.
Hence, 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. This means that the enthalpy change of the overall reaction is the sum of the enthalpy changes of the intermediate reactions.
..........(1)
..............(2)
The final reaction is as follows:
.............(3)
Therefore, adding (1) and (2) we get the final equation (3) and value of
at 298 K will be as follows.
=
+
= -314 kJ + (-80) kJ
= -394 kJ
Thus, we can conclude that
at 298 K for the given process is -394 kJ.
Answer: 
Explanation:
According to the law of conservation of mass, mass can neither be created nor be destroyed. Thus the mass of products must be same as the mass of reactants.
For the conservation of mass, the number of atoms of each element must be same in reactants and products. Thus we need to balance the reaction by writing appropriate stochiometric coefficients.
All the hydrocarbons burn in oxygen to form carbon dioxide and water.Thus the complete balanced equation is:

Answer:
the answer is number 1
Explanation:
because when you make toast you burn it you toast it and there is no way to undo that.