# Displacement Reactions

11SCI - Chemical Reactions

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)