Question

a black R salt on reaction with concentrated hydrochloric acid produces a pungent yellowish green gas which turns moist starch iodide paper black. Name the salt R.​

Answer 1

Answer:

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Answer 2

Explanation:

Black salt is MnO₂ (Manganese dioxide)

The evolved gas is pungent yellowish green in color conform that the gas is Chlorine which turns moist starch iodide paper black.

Reaction 1         MnO₂ + 2 HCl → MnCl₂ + Cl₂(g)↑ +H₂O

                                                             (Yellowish green)

Reaction 2        2KI(aq) + Cl₂(g) → KCl(aq) + I₂(s) Black solid

Chlorine is more stronger oxidizing agent as compare to iodide.During this reaction colorless starch iodide paper turns to black due to the presence of black iodine solid.