Calcium carbonate reacts with phosphoric acid to produce calcium phosphate, carbon dioxide, and water. How many grams of phosphoric acid react with excess calcium carbonate to produce 3.74 grams of Ca3(PO4)2?

Mass Phosphoric acid needed = 2.36 g

Explanation:

3CaCO₃ + 2H₃PO₄ => Ca₃(PO₄)₂ + 3CO₂ + 3H₂O

Given 3.74 g Ca₃(PO₄)₂ => (3.74g/310.2g·mol⁻¹) = 0.0121 mol Ca₃(PO₄)₂

=> 0.0121 mol Ca₃(PO₄)₂ requires 2(0.0121) mol H₃PO₄ = 0.0242 mol H₃PO₄

=> 0.0242 mol H₃PO₄ = (0.0242mol)(98g·mol⁻¹) = 2.36 g H₃PO₄

answer:

the answer is 6 valence electrons.

explanation:

valence is the # of electrons on the outer most shell of an atom.

oxygen has 6.

although, the valency of oxygen is 2, because it only needs to make 2 covalent bonds, or gain 2 electrons, to achieve the stable octet configuration of a noble gas.

that's it!

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