Answer : The enthalpy of the given reaction will be, -1048.6 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.
The main reaction is:

The intermediate balanced chemical reactions are:
(1)

(2)

(3)

(4)

(5)

Now reversing reaction 2, multiplying reaction 3 by 4, reversing reaction 1 and multiplying by 2, reversing reaction 5 and multiplying by 2 and then adding all the equations, we get :
(1)

(2)

(3)

(4)

(5)

The expression for enthalpy of main reaction will be:



Therefore, the enthalpy of the given reaction will be, -1048.6 kJ
Atoms in covalent bonds do combine so as to be stable. As covalent bond consist non metals e.g O2 in this example each atom has vacance of 2 orbitals/ electrons so shairing electrons result their stability
Answer:
Pure Chemistry -- is NOT considered a branch of Chemistry.
Explanation:
Second question is number 4.
Answer:
Combustion reaction
Explanation:
Let's consider the following balanced equation.
CH₄ + 2 O₂ ⇒ CO₂ + 2 H₂O
This reaction is known as a combustion reaction, in which a compound reacts with oxygen to form a compound of carbon and water.
- If the product is carbon dioxide, the combustion is complete.
- If the product is carbon monoxide or carbon, the combustion is incomplete.