Double Replacement Reactions

Cation exchange

Driving Force – Two compounds

Examples Formation of a ppt Ag NO3 + LiBr

Ag+ + Br - AgBr

Formation of a gas HCl + K2SO3

H+ + SO32- H2O + SO2

Formation of a molecular compound HF + SiO2

HF + SiO2 H2O + SiF4

Formation of a ppt – net ionic

1. Determine if the reactants are soluble or insoluble. Soluble – separate into ions, insoluble – keep together.

2. Determine the driving force….which combination of species forms a ppt.

3. Write products with precipitates together and solubles as separated.

4. Cross out species that appear exactly the same on both sides of the equation.

5. Write the Balanced Equation with what remains

Example Copper (II) sulfate is added to sodium sulfide

CuSO4 + Na2S CuS + Na2SO4

Cu2+ + SO42- + 2Na+ + S2- CuS + 2Na+

+ SO42-

Net Ionic Equation Cu2+ + S2- CuS