Explanation:
For the first part,
Reaction equation:
N₂ + 3H₂ → 2NH₃
Given:
Number of moles of NH₃ = 6 moles
Unknown:
Number of moles of N₂ = ?
Solution:
N₂ + 3H₂ → 2NH₃;
From the reaction above, we solve from the known specie to the unknown. Ensure that the equation is balanced;
2 moles of NH₃ is produced from 1 mole of N₂
6 moles of NH₃ will be produced from
mole of N₂
= 3moles of N₂
The number of moles of N₂ is 3 moles
ii.
Given parameters:
Number of moles of sulfur = 2.4moles
Molar mass of sulfur = 32.07g/mol
Unknown:
Mass of sulfur = ?
Solution:
The number of moles of any substance can be found using the expression below;
Number of moles = 
Mass of sulfur = number of moles of sulfur x molar mass
Insert the parameters and solve;
Mass of sulfur = 2.4 x 32.07 = 76.97g
Answer:
Answer D => E°(Mg°/Cu⁺²) = 0.34 + 2.37 = 2.71v
Explanation:
(Oxidation) => Mg°(s) => Mg⁺²(aq) + 2e⁻ E°(Mg°/Mg⁺²) = -2.37 v
(Reduction) => Cu⁺²(aq) + 2e⁻ => Cu°(s) E°(Cu⁺²/Cu°) = +0.34 v
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Net Rxn => Mg°(s) + Cu⁺²(aq) => Mg⁺²(aq) + Cu°(s)
Std Cell Potential (25°C/1Atm) = E°(Redn) = E°(Oxidn) = +0.34v - (-2.37v)
= 0.34v + 2.37v = 2.72v