What do we call a reaction of the form #AB+CD rarr AC+BD#? What occurs when potassium iodide and lead nitrate react?

Question

What do we call a reaction of the form #AB+CD rarr AC+BD#?  What occurs when potassium iodide and lead nitrate react?

Luna Chen · Accepted Answer

This type of reaction is called a double replacement reaction, a double displacement reaction, and a precipitation reaction.

There are multiple names for the reaction that occurs when lead nitrate and potassium iodide combine to form a yellow solid called a precipitate: double displacement, double replacement, and precipitation reaction. A precipitate is formed when the cations and anions in the reactants switch positions in this kind of reaction. #"AB"+"CD"##rarr##"AD"+"CB"#, #"where A and C are cations, and B and D are anions"#. The equation is as follows for this particular reaction: #"2KI(aq)"+"Pb(NO"_3)_2("aq")##rarr##"2KNO"_3("aq")"+PbI"_2("s")"#

Peyton Adams · Answer

The student has performed a #"metathesis"# or #"partner exchange"# reactions, as evidenced by the precipitation of an insoluble solid.

You know the drill: solubility follows a hierarchy. All nitrates and acetates are soluble. All halides are soluble, EXCEPT for #PbX_2#, #Hg_2X_2#, and #AgX#. I would expect a 1st/2nd year student to know this, because they would have done the experiment in the lab. The following equation can be used to depict the metathesis reaction that took place in the test tube: #Pb(NO_3)_2(aq) + 2KX(aq) rarr PbX_2(s)darr+2KNO_3(aq)# In terms of a net ionic equation (potassium and nitrate ions are included): #Pb^(2+)(aq) + 2X^(-)(aq) rarr PbX_2(s)darr#

Cooper Anderson · Answer

undefined Lead nitrate and potassium iodide react to form potassium nitrate and potassium iodide, which is a double displacement reaction.