Net Ionic Equations for dummies...Is there anyone out there that can explain theese on a beginers level...?

Question

I just cannot figure out what I am doing...How do you balance them. I do understand the canceling out of spectators, but when I write out the equation, I get confused on what is written first and which ones stay together and break apart. For example...
CaCl2 (aq) + K3PO4 ----> what goes here??? And once you figure it out and write it all out to see the spectators which ones stay together and which ones part???
PLEASE SOMEONE HELP....

Answer 1

Net ionic equations are most often used when you're forming something insoluble. Refer to the rules in your chemistry text to determine the solubilities of different compounds.

In your example, you have potassium phosphate being added to an aqueous solution of calcium chloride. Both of these compounds are soluble in water, and thus they both dissociate to their respective ions.

(Ca++) + 2(Cl-) + 3(K+) + (PO4---) = ?

From these, you will find upon referencing your solubility table, that calcium and phosphate yield an insoluble compound.

(Ca++) + 2(Cl-) + 3(K+) + (PO4---) = (Ca++PO4---)(s) + 2(Cl-) + 3(K+)

Now you need to balance things out... there's not such thing as CaPO4 by itself, because the charges don't balance. Fortunately, all you need to worry about is the calcium phosphate. A ratio of 3 calciums to 2 phosphates balances the charges, and thus the ratios of the reagents from which those components came must be similarly balanced.

3(Ca++) + 6(Cl-) + 6(K+) + 2(PO4---) = (Ca3(PO4)2)(s) + 6(Cl-) + 6(K+)

This is your total ionic equation. As you can see, the six chlorine ions and six potassium ions don't take part in the reaction, and for your net ionic equation these "spectator" ions are removed, to give you a net ionic equation of:

3(Ca++) + 2(PO4---) = (Ca3(PO4)2)(s)

Anything that I haven't marked as specifically solid (s) is aqueous (aq).

Hope this helps!

Answer 2

Was this question written just like this, or did it say:

CaCl2(aq) + K3PO4(aq) --> ?

I'm going to assume that it did say (aq) after the K3PO4, because it makes more sense that way.

In the first solution, you have Ca2+(aq) ions and 2 Cl-(aq) ions, and in the other solution you have 3 K+(aq) ions and PO4^3-(aq) ions. When you combine those two solutions, Ca3(PO4)2(s) will precipitate. The Cl- ions and the K+ ions will stay in solution because KCl is soluble in water.

So, for your problem, you'll have initially:

3 Ca2+(aq) + 6 Cl-(aq) + 6 K+(aq) + 2 PO43-(aq) --> Ca3(PO4)2(s) + 6 Cl-(aq) + 6 K+(aq).

The Cl- ions and the K+ ions are spectators and can be cancelled.

Some people prefer to balance the equation using the molecular formulas of the compounds and then writing the ionic equation. With practice, you'll be able to do it either way.

Knowing which things will form ions and which will precipitate or remain insoluble requires learning the solubility rules in your text.

Answer 3

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RE:
Net Ionic Equations for dummies...Is there anyone out there that can explain theese on a beginers level...?
I just cannot figure out what I am doing...How do you balance them. I do understand the canceling out of spectators, but when I write out the equation, I get confused on what is written first and which ones stay together and break apart. For example...
CaCl2 (aq) + K3PO4 ----> what goes...

Answer 4

Net Ionic Equations usually produce solids and the rest are left as ions so if you know the solubility of substances, phosphates, PO4 3- are slightly soluble so it would combine with Ca (double replacement reaction) and produce
Ca3(PO4)2 which is a solid and solids stay together in net ionic equations, then the rest are apart and the Ca and PO4 are present in the Net Ionic equation while the other ones arent so 3Ca 2+ + 2PO4 3- >>> Ca3(PO4)2

Answer 5

Equations For Dummies

Answer 6

You only break up soluble compounds, at least that's how I learned it. There are solubility rules that you must memorize in order to balance net ionics quickly, check out: http://www.gonzaga.org/teachers/ceci/Honors%20Solubility%20Rules.htm for a copy of those rules. Believe me, if you take the time to actually memorize that list, well, net ionics will be a whole lot easier!

Answer 7

3CaCl2 + 2K3PO4----> Ca3(PO4)2 + 6KCl
I don't think there are spectators. You need to figure out if any of the bonds are ionic. If so, then one is.