This thermochemical equation needs to be balanced. Hence, option B is correct.
<h3>What is a balanced chemical equation?</h3>
A balanced equation contains the same number of each type of atom on both the left and right sides of the reaction arrow.
The balanced thermochemical equation is:
→ 
Hence, option B is correct.
Learn more about the balanced chemical equation here:
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Anion is an atom with a negative charge
so in this case it woulld be O2-
Atomic mass of helium is 4.002642g/mol
(542000g)/(4.002642g/mol)*6.02*10^23 = 8.15*10^28 atoms