In the reaction 2Mg + O2 -> 2MgO (Mg = 24, MgO = 40 g/mol), what mass of MgO forms from 36 g of magnesium?
Answer and explanation
Correct answer: A. 60 g
- Step 1: Moles of Mg = 36 / 24 = 1.5 mol, and 2 mol Mg gives 2 mol MgO.
- Step 2: Mass of MgO = 1.5 x 40 = 60 g.
Answer
60 g.
Why not the others: '36 g' assumes the product has the same mass as the metal; '52 g' adds a single oxygen atom's mass to the metal; '21.6 g' inverts the mass ratio.
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