Created by StemPy LabAssertion (A): When of magnesium ribbon burns in a closed flask containing of oxygen gas, , 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.
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← Assertion (A): Dalton's atomic theory, which treats a chemical reaction as a reorganisation of atoms, could explain Gay Lussac's finding that two volumes of hydrogen and one volume of oxygen give two volumes of water vapour at the same temperature and pressure.
Reason (R): Avogadro proposed that equal volumes of all gases at the same temperature and pressure contain equal numbers of molecules, and he took the molecules of hydrogen and oxygen to be made of two atoms each.Natural boron is a mixture of two isotopes, with atomic masses 10.01 u and 11.01 u. Its average atomic mass is 10.81 u. A chemist weighs out 10.81 g of natural boron for a tracer experiment, in which she must know how many atoms of each isotope are present. Take NA = 6.022 × 10²³ mol⁻¹. How many atoms of the lighter isotope does this sample contain? →
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