A double displacement reaction, also known as a double replacement reaction or metathesis reaction, occurs when the positive ions or cations and the negative ions or anions of two compounds switch places, forming two new compounds.
The general format of a double displacement reaction is:
AB + CD → AD + CB
Example: when sodium chloride (NaCl) reacts with silver nitrate (AgNO3), a double displacement reaction occurs, leading to the formation of sodium nitrate (NaNO3) and silver chloride (AgCl):
NaCl (aq) + AgNO3 (aq) → NaNO3 (aq) + AgCl (s)
In this reaction, the sodium ion (Na+) from NaCl swaps places with the silver ion (Ag+) from AgNO3, resulting in the formation of sodium nitrate (NaNO3) and silver chloride (AgCl). The silver chloride, being insoluble in water, precipitates out as a solid.
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