What are the spectator ions in the reaction between aqueous solutions of NaOH and Ni(NO3)2?
The correct answer and explanation is:
Correct Answer: The spectator ions in the reaction between aqueous solutions of NaOH and Ni(NO₃)₂ are Na⁺ (sodium ion) and NO₃⁻ (nitrate ion).
Explanation (300 Words):
When two aqueous ionic compounds react, a double displacement reaction often occurs. In this case, the reaction is between sodium hydroxide (NaOH) and nickel(II) nitrate (Ni(NO₃)₂). First, let’s write the balanced molecular equation:
Ni(NO₃)₂ (aq) + 2NaOH (aq) → Ni(OH)₂ (s) + 2NaNO₃ (aq)
This equation shows that nickel(II) hydroxide (Ni(OH)₂) forms as a precipitate (solid), while sodium nitrate (NaNO₃) remains dissolved in solution.
To identify the spectator ions, we write the complete ionic equation:
Ni²⁺ (aq) + 2NO₃⁻ (aq) + 2Na⁺ (aq) + 2OH⁻ (aq) → Ni(OH)₂ (s) + 2Na⁺ (aq) + 2NO₃⁻ (aq)
Now, eliminate the ions that appear unchanged on both sides of the equation. These are the spectator ions, as they do not participate in the actual chemical change:
- Na⁺ (sodium ion)
- NO₃⁻ (nitrate ion)
These ions stay dissolved in the solution and do not take part in the formation of the precipitate.
The net ionic equation, showing only the ions involved in the chemical reaction, is:
Ni²⁺ (aq) + 2OH⁻ (aq) → Ni(OH)₂ (s)
This shows that the actual chemical change involves the combination of nickel(II) ions and hydroxide ions to form insoluble nickel(II) hydroxide.
Conclusion:
The spectator ions are Na⁺ and NO₃⁻. They remain in solution and do not form any new substance. Identifying spectator ions helps in understanding the essential chemistry of the reaction by focusing only on the species that change.