Displacement Reactions

11SCI - Chemical Reactions

Finn LeSueur

2020

Ngā Whāinga Ako

  • To describe what happens in a displacement reaction.

Mahi Tuatahi

  1. Write down the general reaction for a precipitation reaction
  2. What is a precipitate?
  3. Write a word equation for a reaction between sodium hydroxide and copper carbonate
  4. Will a precipitate form during this reaction? (Solubility rules)

Displacement Reactions

\[ \[\begin{aligned} A + BC \longrightarrow B + AC \end{aligned}\]

\]

A reaction where an ion (B) is replaced by another ion (A) in a compound.

Tauria Tahi

A piece of copper is placed into a solution of silver nitrate. The copper replaces the silver, making copper nitrate and silver.

  1. Write a word equation
  2. Write a symbol equation
  1. copper + silver nitrate \(\longrightarrow\) + copper nitrate + silver
  2. \(Cu + AgNO_{3} \longrightarrow Cu(NO_{3})_{2} + Ag\)

Precipitation vs. Displacement

  • Precip: \(AB + CD \longrightarrow AD + CB\)
  • Disp: \(A + BC \longrightarrow B + AC\)
  • We can see how one ion is displaced in a displacemenet reaction, but two ions are displaced in a precipitation reaction. This makes precipitation a “double displacement” reaction.

Tauria Rua

A piece of magnesium is dropped into a copper sulfate solution.

  1. Write a word equation
  2. Write a symbol equation
    • Include states
    • Try to balance it!

Why Does Displacement Occur?

In humans a couple might break up (be displaced) because one partner has found someone more attractive.

In chemistry, one ion displaces another because it is more reactive.

Activity Series

Note which end is the most and least reactive on your resource sheet.

\[ \[\begin{aligned} & \text{Most Reactive} \longrightarrow \text{Least Reactive} \\ & Ca, Mg, Al, Zn, Fe, Pb, (H), Cu, Ag \end{aligned}\]

\]

Tauria Toru

  1. Write a word equation
  2. Write a symbol equation (with states and balanced)