The chemical equation shows the burning of magnesium Mg with oxygen open paren cap o sub 2 close paren to form magnesium oxide MgO 2 Mg plus cap o sub 2 rightarrow 2 MgO The molar mass of cap o sub 2 is 32 point 0 g over mol What mass, in grams, of cap o sub 2 is required to react completely with 4 point 0 0 mol of Mg ?
From the balanced equation, 1 mol of O₂ reacts with 2 mol of Mg. So 4.00 mol Mg requires 4.00 ÷ 2 = 2.00 mol O₂. Multiplying by the molar mass gives 2.00 mol × 32.0 g/mol = 64.0 g, choice C.
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