A precipitate is a solid that forms when a chemical reaction takes place. It occurs when two chemical compounds are mixed and an insoluble compound is formed.
Chemical A (aq) + Chemical B (aq) -> Precipitate (solid)
How to predict a precipitate in a chemical reaction:
Not a precipitate when:
1) Gr 1A ions
2) No3- ions
3) NH4+ ions
To write a precipitate reaction:
Swap chemicals
Add charges
Balance the chemical equation
Predict precipitate.
Na21+CO32- + Pb2+(NO3)21- -> 2 Na1+ NO31- + Pb2+CO32-
Using the rules we can find out if a precipitate is formed and write the proper subscripts.
Pb(NO3)2(aq) + K2CrO4(aq) -> PbCrO4(s) + 2K(NO3)(aq)
Aqueous solution A + Aqueous solution B -> Precipitate + Aqueous solution C
Chemical A (aq) + Chemical B (aq) -> Precipitate (solid)
How to predict a precipitate in a chemical reaction:
Not a precipitate when:
1) Gr 1A ions
2) No3- ions
3) NH4+ ions
To write a precipitate reaction:
Swap chemicals
Add charges
Balance the chemical equation
Predict precipitate.
Na21+CO32- + Pb2+(NO3)21- -> 2 Na1+ NO31- + Pb2+CO32-
Using the rules we can find out if a precipitate is formed and write the proper subscripts.
Pb(NO3)2(aq) + K2CrO4(aq) -> PbCrO4(s) + 2K(NO3)(aq)
Aqueous solution A + Aqueous solution B -> Precipitate + Aqueous solution C
Using a solubility chart we can find out if a chemical compound is soluble or not. It helps us predict precipitates in a chemical reaction. The chart shows whether a chemical compound will dissolve in water or whether it forms a precipitate.
*In the video below, many new rules for solubility are given. As long as your teacher says you will receive a solubility chart, ignore the rules shown. Only the rules above are relevant to the high school course.
Common precipitate colours:
AgI and PbI = Yellow
Mn = Pale Pink
Iron (II) = Green
Iron (III) = Orange/ Brown
Co = Pink
Au = Orange
Cr = Deep Green / Orange / Purple / Murky Green / Red / Yellow / Brown
Cu = Blue
Sulphides = BlackNi = Green
Anything not on this list will usually form a white precipitate.