honestly, who knows. I just want to take a s.h.t.t right now.
Answer : The standard enthalpy of formation of ethylene is, 51.8 kJ/mole
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. That means the enthalpy change of the overall reaction is the sum of the enthalpy changes of the intermediate reactions.
The formation reaction of
will be,

The intermediate balanced chemical reaction will be,
(1)

(2)

(3)

Now we will reverse the reaction 1, multiply reaction 2 and 3 by 2 then adding all the equations, we get :
(1)

(2)

(3)

The expression for enthalpy of formation of
will be,



Therefore, the standard enthalpy of formation of ethylene is, 51.8 kJ/mole
Answer: B
Explanation:
At equilibrium, the rate of the forward reaction is equal to the rate of the reverse reaction, and thus the concentrations of the reactants and products must be constant.
The transfer of energy that occurs when a force is applied over a distance is WORK.
Hope this helps!