3Ca(CH3COO)2(aq) + 2H3PO4(aq) �¨ Ca3(PO4)2(aq) + 6CH3COOH (aq)

reduce in net ionic form... how do you know what to separate? for example, how would i know to separate Ca and PO4 or to keep it together??

You have to be careful how you write the equations, because it makes a big difference. Shouldn't the aq after the calcium phosphate be (s)? Calcium phosphate is not very soluble, as I recall. If in fact it does form a precipate, then you have a chemical reaction.

Ca++(aq) + 2(PO4==)(aq) >> Ca3(PO4)2 (s)

nope, the equation given is all aqueous.

If it is aq, there is no reaction period. Your source is wrong. The solubility of calcium phosphate is less than 1*10^-26.

If in fact it is listed as aq, then there is no reaction, and of course no net ionic equation.

If you get these errors often, I would consider changing instructors, as you will not get the point of chemistry. The point here is that in chemical reactions, certain ions are involved, and others are not. Evidence of a chemical reaction is formation of a precipated, a gas given off, ...
I will assume your instructor erred on the solubility of calcium phosphate.
Good luck

Bob Pursley is correct. Ca3(PO4)2 is insoluble and should be written as Ca3(PO4)2(s) unless it is in acid solution, and the net ionic equation he wrote also is correct. In addition to the two reasons he gave for a reaction to occur (gas formation and insoluble precipitate form), I would add a third for the purpose of writing net ionic equtions as "formation of a weak electrolyte".

To determine what compounds to separate in net ionic form, you need to consider the solubility rules for salts and some general guidelines:

1. Solubility rules: These rules indicate the solubility of common compounds in water. According to the solubility rules, salts containing Group 1 cations (Li+, Na+, K+, etc.) and the ammonium ion (NH4+) are generally soluble and therefore should not be separated in the net ionic equation. However, most other salts, including many compounds containing transition metals, are insoluble or have limited solubility, and their ions should be separated.

2. Spectator ions: In a chemical equation, spectator ions are those ions that do not participate in the chemical reaction. They remain in the same state before and after the reaction. Spectator ions are usually cations or anions from substances that are soluble in water. These ions can be omitted from the net ionic equation.

In the given chemical equation, you are trying to write the net ionic equation for the reaction between Ca(CH3COO)2 and H3PO4. Here's how you can determine what compounds to separate:

1. Write the balanced molecular equation: In the balanced equation provided, Ca(CH3COO)2 and H3PO4 are both aqueous (soluble) compounds, so they remain as complete compounds in solution.

2. Identify the compounds as soluble or insoluble: According to the solubility rules, both Ca(CH3COO)2 and H3PO4 are soluble.

3. Separate the soluble compounds into their ionic forms: Since both compounds are soluble, they will dissociate into their respective ions in water. Ca(CH3COO)2 dissociates into calcium ions (Ca2+) and acetate ions (CH3COO-). H3PO4 dissociates into hydrogen ions (H+) and phosphate ions (PO43-).

4. Identify and remove spectator ions: In this case, the spectator ions are the acetate ions (CH3COO-) and hydrogen ions (H+). They remain in the same state before and after the reaction. These ions can be omitted from the net ionic equation.

5. Write the net ionic equation: After removing the spectator ions, the net ionic equation for the reaction would be:
Ca2+(aq) + PO43-(aq) �¨ Ca3(PO4)2(aq)

In summary, when determining what compounds to separate in net ionic form, consider solubility rules to identify the soluble or insoluble compounds, and remove spectator ions that do not participate in the reaction.