Na2S (Sodium sulfide) is a salt (product) of the reaction between H2S which is a weak acid and NaOH which is a strong base. The reaction that occurs is a neutralization reaction.
2NaOH + H2S → Na2S + 2H2O
The aqueous solution of such a salt is mainly basic (alkaline) due to the presence of additional OH- ions formed by the hydrolysis of the anion. Thus, Na2S is mostly a basic salt such as CaCO3, Na2CO3, etc.
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