Displacement Reactions: Practical Review Quiz

When a piece of magnesium ribbon is added to copper sulfate solution, what is the most likely observation?

• No reaction occurs.

• The blue solution turns colorless and a brown solid forms.

• The solution turns green and bubbles of gas are produced.

• The magnesium turns blue and the solution stays the same.

Answer explanation

When magnesium reacts with copper sulfate, it displaces copper, resulting in a color change from blue to colorless as the copper ions are reduced to solid copper, which appears as a brown precipitate.

Which of these metals will NOT react when placed into a solution of magnesium nitrate?

• Zinc

• Iron

• Copper

• All of the above

Answer explanation

Zinc, iron, and copper are all less reactive than magnesium. Therefore, they will not displace magnesium from magnesium nitrate solution, making 'All of the above' the correct answer.

If iron filings are added to a solution of copper sulfate, a reaction occurs. What is the correct word equation for this?

• Iron + Copper sulfate → Iron sulfate + Copper

• Iron + Copper sulfate → Iron oxide + Copper sulfate

• Iron + Copper sulfate → No reaction

• Iron + Copper sulfate → Copper iron + Sulfate

Answer explanation

The correct reaction occurs when iron reacts with copper sulfate, producing iron sulfate and copper. Thus, the word equation is: Iron + Copper sulfate → Iron sulfate + Copper.

A student adds zinc to iron sulfate solution. They notice the green color of the solution starts to fade. What has happened?

• Iron has displaced the zinc.

• Zinc has displaced the iron because zinc is more reactive.

• The zinc has dissolved to form a gas.

• The iron sulfate has evaporated.

Answer explanation

Zinc is more reactive than iron, so when added to iron sulfate, it displaces the iron, leading to the fading of the green color as iron ions are replaced by zinc ions in the solution.

What would you expect to see if you put a copper nail into a test tube of zinc sulfate?

• The nail turns silver.

• The solution turns blue.

• No visible change.

• Bubbles of hydrogen gas.

Answer explanation

When a copper nail is placed in zinc sulfate, no visible change occurs because copper is less reactive than zinc. Therefore, the copper does not displace zinc from the solution, resulting in no reaction.

Complete the word equation: Magnesium + Zinc sulfate → ________ + ________

• Magnesium sulfate + Zinc

• Magnesium zinc + Sulfate

• Zinc + Magnesium oxide

• No reaction

Answer explanation

The reaction between magnesium and zinc sulfate produces magnesium sulfate and zinc. This is a single displacement reaction where magnesium displaces zinc, resulting in the correct answer: Magnesium sulfate + Zinc.

Why does the blue color fade when magnesium reacts with copper sulfate?

• The magnesium atoms are blue.

• Copper ions (which are blue) are being removed from the solution.

• The solution is getting hotter.

• The sulfate ions are being destroyed.

Answer explanation

The blue color fades because copper ions, which give the solution its blue color, are being removed as magnesium reacts with copper sulfate, leading to a decrease in the blue hue.

Which of the following metals used in the practical is the LEAST reactive?

• Magnesium

• Zinc

• Iron

• Copper

Answer explanation

Copper is the least reactive metal among the options. It does not readily react with acids or oxygen, unlike magnesium, zinc, and iron, which are more reactive and can easily participate in chemical reactions.

What is the correct word equation for the reaction between Zinc and Copper sulfate?

• Zinc + Copper sulfate → Zinc copper + Sulfate

• Zinc + Copper sulfate → Zinc sulfate + Copper

• Zinc + Copper sulfate → Zinc sulfide + Copper

• Copper + Zinc sulfate → Zinc + Copper sulfate

Answer explanation

The correct reaction is Zinc + Copper sulfate → Zinc sulfate + Copper. Zinc displaces copper from copper sulfate, forming zinc sulfate and releasing copper as a product.

In a displacement reaction, which statement is always true?

• A less reactive metal pushes out a more reactive metal from its compound.

• A more reactive metal pushes out a less reactive metal from its compound.

• Both metals must be the same reactivity.

• The solution always turns blue.

Answer explanation

In a displacement reaction, a more reactive metal can displace a less reactive metal from its compound. This is a fundamental principle of reactivity series in chemistry, making the correct choice true.