The mass of Calcium required to complete this reaction is 4.008 g.
In the given reaction mass of product after completion of reaction is 13.614 g that means total mass of constituents before reaction should also be 13.614.
So,
mass of Ca + mass of O₂ + mass of S = mass of CaSO4
Ca + 6.400 g + 3.206 g = 13.614 g
mass of Ca = 13.614 - 9.606 = 4.008 g
Therefore, by law of conservation of mass 4.008 g of Ca is required for the completion of the reaction.
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