1 is D - double-replacements do not make solid metals
2 is A - to have complete combustion the original compound must ONLY have C, H and O
3 is B - the elemental Mg replaces the H in the HCl
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Explanation:
As the given chemical reaction equation is as follows.

Also, it is given that for 2 moles the energy required is 130 kcal. This means that energy required for 1 mole is calculated as follows.
1 mole = 
= 65 kcal
Hence, energy required for 7 moles will be calculated as follows.
Energy required = 
= 455 kcal
Thus, we can conclude that energy required to produce 7.00 mol
on the basis of given reaction is 455 kcal.
Iodine is going to form anions capturing electrons from some other element more electropositive