NET ionic equation

Question

Write the balanced NET ionic equation for the reaction when ZnI₂ and Pb(ClO₄)₂ are mixed in aqueous solution. If no reaction occurs, simply write only NR. Be sure to include the proper phases for all species within the reaction.

Answer 1

Where to start:

Predict the products with phases:

ZnI₂ (aq) + Pb(ClO₄)₂ (aq) → ZnClO₄ (aq) + PbI₂ (s)

To find the phases for each compound, refer to a solubility chart. i.e. on the chart you'll find all chlorates are soluble so if it's with any element, it will be soluble or (aq).

There would be NR if all compounds are (aq), at least one compound must be insoluble.

Make sure the equation is balanced:

ZnI₂ (aq) + Pb(ClO₄)₂ (aq) → Zn(ClO₄)₂ (aq) + PbI₂ (s)

Separate the ions:

Zn⁺² + 2I^- + Pb⁺² + 2ClO₄^- → Zn⁺² + 2ClO₄^- + PbI₂ (s)

You can only separate the (aq) compounds into their ions. PbI₂ stays a compound since it is a solid (s)

Cross off the spectator ions:

Zn⁺² + 2I^- + Pb⁺² + 2ClO₄^- → Zn⁺² + 2ClO₄^- + PbI₂ (s)

2I^- + Pb⁺² → PbI₂

The spectator ions are the ions that cancel out on both sides.

Net ionic equation:

2I^- + Pb⁺² → PbI₂

Answer 2

So the first thing we have to ask ourselves is: are these ionic compound soluble? Soluble means they are able to dissolve in water...

Using our solubility rules (which can be found in your textbook or with a quick google search), we find that ZnI₂ is soluble and Pb(ClO₄)₂ is also soluble. Then using a double displacement reaction (which occurs when we mix two ionic compounds) we would get:

ZnI₂ (aq)+ Pb(ClO₄)₂ (aq) --> Zn(ClO₄)₂ (aq) + PbI₂ (s)

Again, we predict the phases of the products by using our solubility rules, if it is soluble, it is aqueous and if it is insoluble, it is a solid.

When writing our net ionic equation, we can break apart all aqueous species into their corresponding ions and we cannot break apart solid species.

Zn²⁺(aq)+ 2I^- (aq) + Pb²⁺ (aq) + 2ClO₄^- (aq) --> Zn²⁺(aq)+ 2ClO₄^- (aq)+ PbI₂ (s)

We then cancel the ions that are on both product and reactant side: so 2ClO₄^- (aq) and Zn²⁺(aq).

our final answer then would be our net ionic equation which is:

2I^- (aq) + Pb²⁺ (aq) --> PbI₂ (s)