How many moles of electrons are required for denitrifying organism to reduce 78 moles of nitrate to dinitrogen gas?

780 moles e⁻

Explanation:

N⁺⁵ in NO₃⁻ requires 2(5e⁻)  => 1/2 mole N₂(g)

That is, NO₃⁻ + 2(5e⁻/mole N₂ formed) => 1/2N₂

NO₃⁻ + 10e⁻/mole N₂ formed => 1/2N₂

∴ 78 mole NO₃⁻ requires 780 moles e⁻  => 1/2(78) moles N₂ = 39 moles N₂

the answer is c. nacl