Hey there!:
The reactions will produce the respective sulfides as the precipitate. The balencing is done by counting the each individual atom on left hand side and right hande side. Since the valency of Ca is 2 and also S is 2, it will produce Cas, where as S is 2 and sodium is 1, it will form Na2S
a) Ca(OH)₂ (s)+ H₂S (g) -------------> CaS (s) + 2 H₂O
b) Na₂CO₃ (aq) + H₂S (g) -------------> 2 NaS (s) + H₂O + CO₂
I hope this will help !!
