For the reaction 2Mg + O₂ → 2MgO, how many grams of MgO form from 96 g of Mg (all other reactants are in excess)? (Relative atomic masses: H = 1, C = 12, N = 14, O = 16, Na = 23, Mg = 24, Al = 27, S = 32, Cl = 35.5, K = 39, Ca = 40, Fe = 56, Zn = 65.)
Answer and explanation
Correct answer: D. 160 g
- Step 1: Moles of Mg = 96/24 = 4 mol.
- Step 2: The mole ratio Mg : MgO is 2 : 2, so 4 mol of MgO forms.
- Step 3: Mass = 4 x 40 = 160 g.
Answer
160 g.
Why not the others: 96 g: the mass of product was assumed equal to the mass of reactant. 4 g: the moles of product were found but not converted to grams. 320 g: the mole ratio was inverted.
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