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own, , Calculate the number of molecules of sulphur (Ss) present in 16g of solid sulphur., , Answer 10:, 1 mole of solid sulphur (Ss) = 8 x 32g = 256g, , 6.022 x 108 molecules, 2x 1028, 256, , , , ie., 256g of solid sulphur contain:, Then, 16g of solid sulpur contains, , , , x 16 molecules, , = 3.76 x 10” molecules (approx), , owning), , Calculate the number of aluminium ions present in 0.051g of aluminium oxide., (Hint: The mass of an ion is the same as that of an atom of the same element. Atomic mass of Al, er), Answer 11:, 1 mole of aluminium oxide (Al2O3) = 2 x 27 + 3 x 16 = 102g, i.e., 102g of Al2O3 = 6.022 x 10° molecules of AlO3, Then, 0.051 g of Al2Os contains = somo’ x 0.051 molecules, = 3.011 x 10% molecules of ALO;, The number of aluminium ions (Al**) present in one molecules of aluminium oxide is 2., Therefore, The number of aluminium ions (Al**) present in, , 3.11 x 107° molecules (0.0512) of aluminium oxide (Al2O3) = 2 x 3.011 x 107°, = 6.022 x 107