Q41Long answer
Compute the difference in masses of one mole each of aluminium atoms and one mole of its ions. (Mass of an electron is 9.1×10–28 g). Which one is heavier?
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Mass of 1 mole of aluminium atom = the molar mass of aluminium = 27 g mol–1 An aluminium atom needs to lose three electrons to become an ion, Al3+ For one mole of A13+ ion, three moles of electrons are to be lost. The mass of three moles of electrons = 3 × (9.1×10–28 ) × 6.022×1023 g = 27.3 × 6.022 ×10–5 g = 164.400 ×10 –5 g = 0.00164 g Molar mass of Al 3+ = (27–0.00164) g mol–1 = 26.9984 g mol–1 Difference = 27 – 26.9984 = 0.0016 g ANSWERS 107