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Sodium metal is dissolved in liquid ammonia at low temperature. Which of the following statements about the resulting solution is/are correct?

1. Sodium metal cannot be recovered from this solution on evaporation.
2. The liquid ammonia solution becomes a good conductor of electricity.
3. The liquid ammonia solution becomes paramagnetic.
4. A blue-coloured solution is obtained.

Correct answer: A blue-coloured solution is obtained.

Solution

When Na dissolves in liquid NH3: Na -> Na+(am) + e-(am). Solvated electrons give the solution a characteristic blue colour at low concentration (bronze at high). The solution IS a good conductor (B true), IS paramagnetic due to unpaired solvated electrons (C true), and IS blue (D true). On evaporation, the ammonia evaporates and Na metal is recovered (A is false). The question asks for which are correct — B, C, D are all correct, but if only one answer is needed per convention, D is most distinctively 'always correct'. Multiple correct: B, C, D.

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