Created by StemPy LabNatural boron is a mixture of two isotopes, with atomic masses and . Its average atomic mass is . A chemist weighs out of natural boron for a tracer experiment, in which she must know how many atoms of each isotope are present. Take . How many atoms of the lighter isotope does this sample contain?
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← Assertion (A): When 1.00 g of magnesium ribbon burns in a closed flask containing 1.00 g of oxygen gas, 2Mg + O₂ → 2MgO, all the magnesium is used up and some oxygen is left over (atomic masses: Mg 24, O 16). Reason (R): In any reaction, the reactant with the smaller molar mass is the limiting reagent, because a gram of it holds more moles.Methanal, HCHO, and glucose, C₆H₁₂O₆, have the same empirical formula, CH₂O. Each is burnt completely in excess oxygen to carbon dioxide and water. Atomic masses in g mol⁻¹: H 1, C 12, O 16. Statement I: Burning 1 mol of methanal and 1 mol of glucose gives the same number of moles of carbon dioxide. Statement II: Burning 3.0 g of methanal and 3.0 g of glucose gives the same mass of carbon dioxide, 4.4 g each. →
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