Question

Write a net ionic equation for the reaction that occurs when excess hydroiodic acid and nickel(II) sulfide are combined.

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Answer 1

Step-by-step explanation:

Step 1: Write the balanced "molecular" equation:

`2HI(aq) + NIS (s) → NiI₂(aq) + H₂S(g)`

Step 2: H₂S is written in molecular form. Consult the solubility and net ionic equation rules on the information page to determine which of the other substances will dissociate:

`2HI(aq) + NIS (s) → NiI₂(aq) + H₂S(g)`

yes no yes

Step 3: Dissociate all soluble salts, strong acids, and strong bases (except calcium hydroxide). Leave together all "not soluble" salts and weak acids or bases:

`{2H₃O}^( + ) (aq) + {2I}^( - ) (aq) + NiS(s)→ { Ni}^(2 + )(aq) + {2I}^( - )(aq) + H₂S(g) + 2H₂O(l)`

Step 4: Cross out "spectator ions" that appear on both sides of the reaction (these ions do not participate in the chemistry) and rewrite the "net" reaction using the smallest possible coefficients:

`{2H₃O}^( + ) (aq) + NiS(s) → { Ni}^(2 + ) (aq) + H₂S(g) + 2H₂O(l)`