9.5 Reaction Between Na and Cl

Chemical Concepts Demonstrated: Metal/nonmetal/ionic chemistry

Demonstration:

A large glass flask with sand covering the bottom is filled with Cl2 gas. Hot sodium metal is plunged into the flask.

Observations:

    The metal bursts into flames.

Explanation (including important chemical equations):

    The sodium reacts with the chlorine in the flask to create NaCl.   The reaction's driving forces are shown below:

    Heat of Sublimation [Na(s) -> Na(g)]: 107.3 kJ/mol

    1st Ionization Energy [Na(g) -> Na⁺(g) + e^-]: 495.8 kJ/mol

    Bond Dissociation Enthalpy [1/2 Cl₂(g) -> Cl(g)]: 121.7 kJ/mol

    Electron Affinity [Cl(g) + e^- -> Cl^-(g)]: -348.8 kJ/mol

    Lattice Energy [Na⁺(g) + Cl^-(g)]: -787.3 kJ/mol

    Overall reaction [Na(s) + 1/2 Cl₂(g) -> NaCl(s)]: -411.3 kJ/mol