precipitation reactions Flashcards
what are precipitates
When two solutions of ionic compounds are mixed, the ions sometimes react to form an insoluble solid called a precipitate.
example of a precipitate
when a sodium hydroxide solution is mixed with a copper sulfate solution, a pale blue precipitate is produced.
This solid is copper hydroxide.
The ions recombine to form a new product.
why do the precipitates form
The solid forms because there is a stronger attraction between the ions forming the solid than there is between the ions and the solvent.
how can a precipitation be identified
A precipitate can be identified by checking the solubility table to see which of the products formed are insoluble.
When a sodium chloride solution (NaCℓ) is mixed with a silver nitrate solution (AgNO3), the ions can recombine to:
Na+ and NO3- combine to form sodium nitrate (NaNO3)
Ag+ and Cℓ- combine to form silver chloride (AgCℓ)
Silver chloride is insoluble in water, so forms a white precipitate
when the two ionic solutions have recombined, does the two new recombined products need to be ionic in a precipitation reaction
yes (all bonds have to be ionic)
the positive element bonds with negative element
what ions are shown in a ionic equation
Ionic equations only show the ions that form a precipitate.
They change from free ions to ions locked in solid lattice.
what are spectator ions
the ions that stay dissolved in the solution and do not form a precipitate are called spectator ions (these ions does not change the reaction)
write an equation for. When a potassium chloride solution (KCℓ) is mixed with a silver nitrate solution (AgNO3), only the silver and chloride ions are reacting to form silver chloride.
KCℓ(aq) + AgNO3(aq) -> AgCℓ(s) + KNO3(aq)
The other ions are spectator ions and are not involved in the reaction, so we can shorten the equation to:
Cℓ-(aq) + Ag+(aq) -> AgCℓ(s)
