Can someone explain a single replacement and double displacement reactions?

Question

possibly explain what they are and give an example

Thanks for your help

Answer 1

In a single replacement A+BC-->AC+B. In other words, A replaces B to form a compound with C. For example,

Mg + 2HCl --> MgCl2 + H2.

In a double replacement, AB + CD --> AD + CB. Both species swap with one another. For example,

AgNO3 + NaCl --> AgCl + NaNO3.



Hope that helped.

Answer 2

The only problem with Amy T's examples is that they aren't actual reactions.  In each case, nothing will actually happen.

In the first reaction if NaCl is in aqueous solution the K(s) will react with the water, so will Na(s).  Therefore Na will never form.

In the second, for there to be an actual reaction, there must be an insoluble product.  There's not one.  That is why it is so important to memorize the solubility rules.

The best way to represent single and double replacement reactions is with ionic equations.  Then you can see if something does indeed happen.

For instance, this reaction does occur:

Cu(s) + 2AgNO3(aq) -->  Cu(NO3)2 + 2Ag(s)

The nitrate is the spectator ion.  The actual reaction is between Cu and silver ion

Cu(s) + 2Ag+ --> Cu2+ + 2Ag(s)

Or consider the reaction where silver chloride solid is formed:

AgNO3(aq) + NaCl(aq) --> AgCl(s) + NaNO3(aq)

The Na+ and NO3- ions really don't do anything.  The only reaction is between silver ions and chloride ions.

Ag+ + Cl- -->  AgCl(s)

For a double replacement reaction to actually occur there must be an insoluble (or undissociated) product.

Answer 3

single replacement is where only one element moves.. for example: NaCl+ K= KCl + Na

double displacement is a switch between two elements.

NaCl +KOH= NaOH +KCl