The answer is C. Valence Electrons
They have to form a chemical bond in order to brake them down first
We use the radioactive decay formula to solve this problem. It is expressed as:
An = Aoe^-kt
where An is the amount left in time t, Ao is the initial amount, k is the constant.
We first find the value of k from the half-life data. We do as follows:
An = Aoe^-kt
0.5 = e^-k(5730)
k = 1.21x10^-4
An = Aoe^-kt
1/4 = e^-1.21x10^-4t
t = 11456.98 years
Explanation:
The net equation will be as follows.
So, we are required to find for this reaction.
Therefore, steps involved for the above process are as follows.
Step 1: Convert K from solid state to gaseous state
, = 89 kJ
Step 2: Ionization of gaseous K
, = 418 KJ
Step 3: Dissociation of gas into chlorine atom
.
, = 122 KJ
Step 4: Iozination of chlorine atom.
, = -349 KJ
Step 5: Add ion and ion formed above to get KCl
.
, = -717 KJ
Now, using Born-Haber cycle, value of enthalpy of the formation is calculated as follows.
= 89 + 418 + 122 - 349 - 717
= - 437 KJ/mol
Thus, we can conclude that the heat of formation of KCl is - 437 KJ/mol.