Metals and Non-metals · Lesson 6 of 13
How Do Metals React With Solutions Of Other Metal Salts?
“The reactivity series turns metal displacement into a predictable hierarchy instead of a guessing game.”
• Explain displacement reactions between metals and salt solutions. • Use observations with iron, copper and their salt solutions to compare reactivity. • State and use the complete reactivity series given in the chapter. • Predict whether a displacement reaction will occur. • Use the position of hydrogen to predict whether a metal can displace hydrogen from dilute acids.
Displacement reactions give direct evidence of relative reactivity. If one metal pushes another metal out of its compound, the displacing metal is more reactive.
How Do Metals React With Solutions Of Other Metal Salts?
Copper wire in iron sulphate does not displace iron. Iron placed in copper sulphate does react: iron forms iron sulphate while copper is deposited.
Displacement And Relative Reactivity
If A displaces B from a salt of B, A is more reactive than B. A less reactive metal cannot displace a more reactive one under the same rule.
Problem
Metal X displaces copper from copper sulphate. What follows?
- 1.X has replaced copper in its compound.
- 2.Displacement requires X to be more reactive than copper.
- 3.Therefore X is more reactive than copper.
The Reactivity Series
The Reactivity Series is a list of metals arranged in decreasing order of reactivity.
The series is potassium, sodium, calcium, magnesium, aluminium, zinc, iron, lead, hydrogen, copper, mercury, silver and gold. Hydrogen is included as a reference.
Predicting Displacement Reactions
Locate the free metal and the metal inside the salt. If the free metal is higher, displacement can occur. If it is lower, no displacement is predicted.
Problem
Will zinc react with iron(II) sulphate?
- 1.Zinc lies above iron.
- 2.Zinc is more reactive.
- 3.A more reactive metal can displace a lower one.
- 4.Therefore Zn + FeSO₄ → ZnSO₄ + Fe.
Problem
Will silver displace zinc from zinc sulphate?
- 1.Silver lies below zinc.
- 2.Silver is less reactive.
- 3.It cannot displace zinc.
- 4.No displacement reaction is predicted.
Position Of Hydrogen
Metals above hydrogen can displace hydrogen from suitable dilute acids. Metals below hydrogen, such as copper, silver and gold, do not follow that displacement pattern.
Connecting Earlier Reactions
The series also helps organise earlier observations. Highly reactive metals tend to react more vigorously with oxygen and water. Salt-solution displacement is especially useful when oxygen or water reactions do not clearly distinguish two metals.
Quiz
If A displaces B from B's salt, what does this show?
Which metal is more reactive in Fe + CuSO₄ → FeSO₄ + Cu?
Which metal lies above iron in the series?
What is hydrogen used for in the series?
Which metal can displace copper from copper sulphate?
Practice Problems
- Write the equation for iron reacting with copper sulphate and identify the displaced metal.
- Predict whether copper displaces iron from iron sulphate.
- Predict whether aluminium displaces zinc from zinc sulphate and explain step by step.
- Predict whether silver displaces copper from copper sulphate.
- Use hydrogen's position to explain why zinc reacts with dilute hydrochloric acid but copper does not.
- Arrange Mg, Zn, Fe, Cu and Ag in decreasing reactivity.
Key Takeaways
• A more reactive metal displaces a less reactive metal from its salt solution. • Displacement experiments provide direct evidence for comparing reactivity. • The reactivity series arranges metals in decreasing order from potassium toward gold. • Metals above hydrogen can displace hydrogen from suitable dilute acids. • The reactivity series connects observations from oxygen, water, acid and salt-solution reactions.