differentiate b/w single displacement reactions and double displacement reactions (3 points)

Asked by  | 18th Mar, 2012, 06:39: PM

Expert Answer:

Single displacement: This is when one element trades places with another element in a compound. These reactions come in the general form of:

A + BC? AC + B

A and B must be either:

  • different metals (hydrogen's behavior as a cation renders it as a metal here), in which case C represents an anion; or
  • halogens, in which case C represents a cation.

One example of a single displacement reaction is when magnesium replaces hydrogen in water to make magnesium hydroxide and hydrogen gas:

Mg + 2 H2O  ?Mg(OH)2 + H2

Double displacement: This is when the anions and cations of two different molecules switch places, forming two entirely different compounds. These reactions are in the general form:

AB + CD? AD + CB

One example of a double displacement reaction is the reaction of lead (II) nitrate with potassium iodide to form lead (II) iodide and potassium nitrate:

Pb(NO3)2 + 2 KI ? PbI2 + 2 KNO3

Reactions that can be classified as double displacements include precipitation reactions, neutralization reactions and gas forming reactions. 

Answered by  | 19th Mar, 2012, 01:16: PM

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