Question

What are the molecular, complete ionic, and net ionic equations for the reaction between `"CuCl"_2"` and `"H"_4"SiO"_4"`?

Answer 1

`"2CuCl"_2"(aq)` + `"H"_4"SiO"_4"(aq)` `rarr` `"Cu"_2"SiO"_4"(s)` + `"4HCl"(aq)`

Explanation:

If you are being asked to find the molecular, complete ionic, and net ionic equations, you are dealing with a double replacement/displacement reaction. I will continue answering the question using the term double replacement, though displacement is just as valid.

During double replacement reactions, the cations (positively charged ions) and anions (negatively charged ions) of two different compounds switch places. The generic equation is AB + XY `rarr` AY + XB, where A and X are the cations, and B and Y are the anions. The products of a double replacement reaction must include a precipitate (insoluble solid), water, or gas.

The names and symbols of the ions are the copper (II) ion, `"Cu"^"2+"`, the chloride ion, `"Cl"^"-"`, the hydrogen ion, `"H"^+`, and the silicate ion, `"SiO"_4^"4-"`.

The molecular equations is

`"2CuCl"_2"(aq)` + `"H"_4"SiO"_4"(aq)` `rarr` `"Cu"_2"SiO"_4"(s)` + `"4HCl"(aq)`

In this reaction, a precipitate (solid) was produced, so this is a double replacement reaction.

The word equation for this reaction is two moles of aqueous copper (II) chloride plus one mole of aqueous silicic acid, `"H"_4"SiO"_4"(aq)`, produce one mole of solid copper (II) silicate plus four moles of aqueous hydrochloric acid.

The complete ionic equation includes all of the ions, plus the precipitate (solid).

`"2Cu"^"2+"(aq)` + `"4Cl"^"-"(aq)` + `"4H"^+"(aq)` + `"SiO"_4^"4-"(aq)` `rarr` `"Cu"_2"SiO"_4"(s)` + `"4H"^+"(aq)` + `"4Cl"^"-"(aq)`

The net ionic equation includes only the ions that formed the precipitate, and the precipitate.

`"2Cu"^"2+"(aq)` + `"SiO"_4^"4-"(aq)` `rarr` `"Cu"_2"SiO"_4"(s)`

Here is another example which illustrates how to write a net ionic equation.

video from: Noel Pauller