How many moles are there in 80 g of MgO? (molar mass 40 g/mol)
Answer and explanation
Correct answer: B. 2 mol
- Step 1: Moles = mass ÷ molar mass. Step 2. 80 ÷ 40 = 2 mol. Answer: 2 mol. Why not the others: 3200 mol is what you get if you multiply the mass by the molar mass. 0.5 mol is what you get if you invert the ratio. 40 mol is what you get if you subtract the molar mass.
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