with Ionic Equation Writing

1. Redox Reaction There is a change in oxidation number

between reactant side and product side

Ca + Fe3(PO4)2 Ca3(PO4)2 + FeOxidation #Ca = 0Fe2+ PO4

3-Ca2+ PO4

3-

Fe = 0Diatomics have an oxidation # of zero

2. Non-Redox Reaction No change in oxidation number between

reactant side and product side

NaCl + K2SO4 Na2SO4 + KClOxidation #Na+ Cl-K+ SO4

2-Na+ SO4

2-

K+ Cl-Typically 2 ionic compounds reacting together

If a compound is soluble in water,

it exists as ions in water.

If a compound is insoluble in water,

It exists as a precipitate (solid) in water

We are going to assume all reactant compounds are soluble in water as we practice making ions…..

If soluble in water: NH4F will exist as

◦NH4+

◦F-

NH4+

F-

If soluble in water: H2CO3 will exist as

◦H+ ◦CO3

2-

H+

H+

CO32-

But really 2H+

If soluble in water: Al(NO3)3 will exist as

◦Al3+ ◦NO3

-

NO3-

Al3+

NO3-

But really 3NO3-

NO3-

1. Both reactants are soluble in water Mark with (aq)

2. Must determine if products are soluble or insoluble using solubility rules

If soluble – mark with (aq) If insoluble – mark with (s)

Two elements in reactants take the place of each other

AB + CD AD + CBAgNO3(aq)+ NaCl(aq) AgCl(s) + NaNO3(aq)

Zn(OH)2(aq) + 2HCl(aq) ZnCl2(aq) + 2H2O(l)

Reactants must be two ionic compounds or acids.

Usually in aqueous solution Na2SO4(aq) + CaCl2(aq) The positive ions change place. Na2SO4(aq)+ CaCl2(aq)Ca+2 SO4

2- + Na+1Cl-1

Na2SO4(aq) + CaCl2(aq) CaSO4(s) + 2NaCl(aq)

Will only happen if one of the products:

◦doesn’t dissolve in water and forms an insoluble solid (s) (precipitate).

◦is a gas that bubbles out.◦is water (H2O) (neutralization reaction).

Insoluble salt = a precipitate◦Solubility rules (see handout for explanation)

CASH N GiAm

KCl Na2SO4 CaSO4 AgSO4 Na2CO3 MgS

KCl(aq) Na2SO4(aq) CaSO4(s) AgSO4(s) Na2CO3(aq) MgS(s)

Many reactions occur in water- that is, in aqueous solution

Many ionic compounds “dissociate”, or separate, into cations and anions when dissolved in water

Now we can write a complete ionic equation & net ionic equation.

Example:AgNO3(aq) + NaCl (aq) AgCl (s) + NaNO3(aq)

1.this is the full equation (molecular equation)

2. now write it as an complete ionic equation Anything (aq) will dissociate (separate into ions)

Ag+ + NO3- + Na+ + Cl- AgCl(s) + Na+ + NO3

-

Complete ionic equation:Ag+ + NO3

- + Na+ + Cl- AgCl(s) + Na+ + NO3-

3. can be simplified by eliminating ions not directly involved in making the reaction happen (spectator ions) = net ionic equation

Ag+ + Cl- AgCl(s)Na+ and NO3

- are spectator ions and are removed in the net ionic equation.