Answer: " 1.8 * 10²⁴ molecules of O₂ " .
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3.0 moles O₂ * (6.02 * 10²³ molecules O₂ / 1 mol O₂) =
[ (3.0) *(6.02 * 10²³) ] molecules O₂
= 1.806 * 10²⁴ ; round to 2 significant figures.
= 1.8 * 10²⁴ molecules of O₂ .
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