What is the net ionic equation of this (including phases)
cu(clo4)2 (aq) + na2s ==> cus(s)+2naclo4(aq) ?

Ionic equation is:

Cu+1 + ClO4-1 + 2Na+1 + S-2 > CuS(s) + 2Na+1 + 2ClO4-1

If we balance the both sides to get the net ionic equation:

Cu+1 + S-2 > CuS(s) + ClO4-1

Cu²⁺(aq) + 2(ClO₄)⁻(aq) +  2Na⁺(aq)  + S²⁻(aq) → CuS (s) + 2Na⁺(aq) + 2(ClO₄)⁻(aq)

Explanation:

The net ionic equation is the equation of the ions that are dissolved in liquid. In this case water, because of the phase aqueous (aq). So, the aqueous ionic compounds will be a break in their ions, which can be made by changing the subscript to be the charge of the other ion:

Cu(ClO₄)₂   → Cu²⁺ + (ClO₄)⁻

Na₂S  →  Na⁺  + S²⁻

NaClO₄ → Na⁺ + (ClO₄)⁻

So, the reaction must be:

Cu²⁺(aq) + 2(ClO₄)⁻(aq) +  2Na⁺(aq)  + S²⁻(aq) → CuS (s) + 2Na⁺(aq) + 2(ClO₄)⁻(aq)

the answer is d. 74.02

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