Displacement Reactions Displacement Reactions Lets look at the

Displacement Reactions

Displacement Reactions • Lets look at the reaction between chlorine and potassium bromide • When chlorine is bubbled through potassium bromide solution (colourless), the liquid turns red-brown, because bromine forms. • The reaction is: Cl 2(g) 2 KBr(aq) 2 KCl(aq) Br 2(g)

Displacement Reactions • Bromine has given up electrons to chlorine. • The bromine has been oxidized and the chlorine has been reduced. • The Ionic Equation is: Cl 2(g) 2 Br -(aq) 2 Cl -(aq) Br 2(g)

Displacement Reactions • In effect chlorine has pushed bromine out of the potassium compound and taken its place. • It has displaced bromine. • Redox reactions like these, where one element displaces another from a dissolved compound (solution), are called displacement reactions.

Displacement of One Metal by Another. • An iron nail is placed in copper II sulfate solution. • Soon copper appears on the nail and the solution turns green. • Here iron and copper are competing to be the compound in solution. Iron wins. • It displaces copper from copper II sulfate solution. A green iron II sulfate solution is formed.

The Equation Fe(s) Cu. SO 4(aq) Blue Fe. SO 4(aq) Cu(s) Green • the ionic equation is: Fe(s) Cu 2+(aq) Fe 2+ (aq) Cu(s)

Displacement Reactions • Other metals displace less reactive metals in the same way. • A metal will always displace a less reactive metal from solutions of its compounds. • When copper wire is placed in silver nitrate solution, the solution turns blue and crystals of silver form on the wire. • Which metal is more reactive?

Remember the Activity Series • Potassium > Sodium > Lithium > Calcium > Magnesium > Aluminium > Zinc > Iron > Lead > (hydrogen) > Copper > Silver > Gold • Copper is more reactive. Cu(s) Ag. NO 3(aq) Cu(NO 3)2(aq) Ag(s)

Try This…. • What would you see if you added zinc to copper sulfate solution? • Hint zinc sulfate is colourless.

Now Try This…… • Tin does not react with iron II oxide. But it reduces lead II oxide to lead. • Arrange tin, iron and lead in order of decreasing reactivity. • Iron > tin > lead

Displacement of Hydrogen • Some metals will react with dilute acid. • These metals displace Hydrogen from the acid. Mg(s) HCl(aq) Mg. Cl 2(aq) H 2(g)