Single Displacement Reactions (with Nonmetals)
Single displacement reactions are always a reaction between a compound and an element. If the element is nonmetal, the equation for the reaction has the following general form:
Compound AB + Element C –> Compound AC + Element B
Note that the nonmetal C displaces nonmetal B in the compound AB. This reaction will only occur if nonmetal C is more active than nonmetal B. If nonmetal B is more active than nonmetal C then no reaction will occur.
Activity Series of the Halogens (from most active to least active)
Example: Consider the reaction between potassium iodide and liquid bromine. Bromine is more active than iodine, so bromine can displace iodine in a compound as shown below:
(Note that this equation is not balanced)
To balance this equation note there are 2 Br atoms on the left, so a coefficient of 2 is needed in front of the KBr in order to have 2 Br atoms on the right. Then a coefficient of 2 is needed in front of the KI in order to balance the 2 K atoms and the 2 I atoms on the right: