The Eθ(M2+/M) value for copper is positive (+0.34V). What is possibly the reason for this? (Hint: consider its high ΔaHθ and low ΔhydHθ)
The Eθ(M2+/M) value of a metal depends on the energy changes involved in the following:
1. Sublimation: The energy required for converting one mole of an atom from the solid state to the gaseous state.
`M_(s) -> M_(g) triangle_sH("Sublimation energy")`
2. Ionization: The energy required to take out electrons from one mole of atoms in the gaseous state.
`M_(g) -> M_(" "(aq))^(2+) triangle_iH("Ionization energy")`
3. Hydration: The energy released when one mole of ions are hydrated.
`M_(" "(g))^(2+) -> M_(" "(aq))^(2+) triangle_"hyd"H("Hydration energy")`
Now, copper has a high energy of atomization and low hydration energy. Hence, the Eθ(M2+/M) value for copper is positive.
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