JAMB - Chemistry (2005 - No. 2)

Which of the following ions require the largest quantity of electricity for discharge at an electrode?
4.0 moles of Cl-
3.0 moles of Na+
2.5 moles of Cu2+
2.0 moles of Al3+

Explanation

To get the quantity of electricity for discharge at an electrode for each ions, we multiply the number of electrons by the number of moles, since 1 mole = 1F

  • 4.0 moles of Cl\(^-\)  → 1e\(^-\) x  4 = 4F
  • 3.0 moles of Na\(^+\)  → 3e\(^-\) x 1 = 3F
  • 2.5 moles of Cu\(^{2+}\) → 2e\(^-\) x 2.5 = 5F
  • 2.0 moles of Al\(^{3+}\)  → 3e\(^-\) x 2  = 6F.  The Ions that require the largest quantity of electricity for discharge at an electrode is the Al\(^{3+}\).

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