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Question

Determine the mass of copper (I) sulfide which can be oxidized with 7.8 x 10²³ oxygen molecules. Reaction products are copper (I) oxide and sulfur (IV) oxide.

Answer 1

First the balanced reaction: 2 Cu₂S + 5 O₂ --> 2 Cu₂O + 2 SO₄. Number of moles of O₂ = (7.8 x 10²³ molecules) / (6.022 x 10²³ molecules/mole) = 1.2₉₅ moles (subscripted numbers are non-significant digits but are kept for computational accuracy). Stoichiometry: (1.2₉₅ mol O₂) * (2 mol Cu₂S /5 mol O₂) * (159.2g Cu₂S /1 mol Cu₂S) = 82.₅ g Cu₂S.