I believe the answer is 3 - He hypothesized that all substances can be broken down into a smallest part called the atom.
The reaction;
O(g) +O2(g)→O3(g), ΔH = sum of bond enthalpy of reactants-sum of food enthalpy of products.
ΔH = ( bond enthalpy of O(g)+bond enthalpy of O2 (g) - bond enthalpy of O3(g)
-107.2 kJ/mol = O+487.7kJ/mol =O+487.7 kJ/mol +487.7kJ/mol =594.9 kJ/mol
Bond enthalpy (BE) of O3(g) is equals to 2× bond enthalpy of O3(g) because, O3(g) has two types of bonds from its lewis structure (0-0=0).
∴2BE of O3(g) = 594.9kJ/mol
Average bond enthalpy = 594.9kJ/mol/2
=297.45kJ/mol
∴ Averange bond enthalpy of O3(g) is 297.45kJ/mol.
Answer : The change in boiling point is, 
Explanation :
Formula used :
where,
= change in boiling point = ?
i = Van't Hoff factor = 3 (for MgI₂ electrolyte)
= boiling point constant for water = 
m = molality = 0.615 m
Now put all the given values in this formula, we get
Therefore, the change in boiling point is,
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