Addition of dilute hydrochloride acid to an aqueous solution of a crystalline salt yield a yellow precipitate and a gas which turned dichromate paper green. The crystalline salt was probably?

  • A Na2SO4
  • B Na2S
  • C Na2S2O3.5H2O
  • D Na2CO3
  • E NaHCO3

The correct answer is C. Na2S2O3.5H2O

No explanation given
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