The phase change between white tin and gray tin is difficult to observe directly. Both substances can be burned, however. From these equations, calculate AHⓇ for the conversion of gray tin into white tin: Sn(s, white) + O2(g) + SnO2(g) AH = -580.69 kJ
Sn(s, gray) + O2(g) + SnO2(g) AH° = -582.78 kJ
AH = kJ

Thus for the conversion of gray tin to white tin is -20.9 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.

According to this law, enthalpy change of the overall reaction is the sum of the enthalpy changes of the intermediate reactions.

The final reaction is

The intermediate balanced chemical reaction will be,

     (1)

      (2)    

substarcting (2) form (1) we get

atomic mass = 39

number of neutrons = 20

number of protons= 19

electronic configuration = 1s2 2s2 2p6 3s2 3p6 4s1

the number of electron in first shell = 2

number of electrons in n=3 shell = 8