<u>Answer:</u> The activation energy of the reverse reaction is 47 kJ/mol
<u>Explanation:</u>
The chemical equation for the decomposition of dinitrogen pentaoxide follows:

We are given:
Activation energy of the above reaction (forward reaction) = 102 kJ/mol
Enthalpy of the reaction = +55 kJ/mol
As, the enthalpy of the reaction is positive, the reaction is said to be endothermic in nature.
To calculate the activation energy for the reverse reaction, we use the equation:

where,
= Activation energy of the forward reaction = 102 kJ/mol
= Activation energy of the backward reaction = ?
= Enthalpy of the reaction = +55 kJ/mol
Putting values in above equation, we get:

Hence, the activation energy of the reverse reaction is 47 kJ/mol
I think it’s Labeled or numbered....
The picture of Au₃N is attached below.
The first part of the picture shows the formation of Au and N ions.
Formation of Au⁺¹ :
As Gold has one valence electron in 6s¹ therefore, it will loose it to form Au⁺¹. In case of Au₃N three atoms of Au looses three electrons to form three Au⁺¹ ions.
Formation of N⁻³ :
As Nitrogen has 5 valence elctrions therefore, it will gain three electrons that lost by Au to form Nitrite (i.e. N⁻³)
Formation of Au₃N:
Three cations of Au⁺ combines with one anion of N⁻³ to form a neutral ionic compound i.e. Au₃N as shown in second part of the picture.
First, we determine the energy released by the reaction using the heat capacity and change in temperature as such:
Q = cΔT
Q = 32.16 * 0.42
Q = 13.51 kJ
Next, we determine the moles of ammonia formed as the heat of formation is expressed in "per mole".
Moles = mass / molecular weight
Moles = 5/17
Moles = 0.294
Heat of formation = 13.51 / 0.294
The heat of formation of ammonia is 45.95 kJ/mol