Solutions of copper sulphate, iron sulphate and zinc sulphate are prepared and marked I, II and III respectively. Few pieces of aluminium are added to each solution. After some time a change will be observed in

Q: Solutions of copper sulphate, iron sulphate and zinc sulphate are prepared and marked I, II and III respectively. Few pieces of aluminium are added to each solution. After some time a change will be observed in

The correct option is **D**. A change will be observed in all three solutions because aluminium ($Al$) is more reactive than copper ($Cu$), iron ($Fe$), and zinc ($Zn$), allowing it to displace them from their respective sulphate solutions.

Chemical Reactions and Equations

Types of Chemical Reactions

Options

(A)I and II

(B)II and III

(C)III and I

(D)All the three

Official Answer

The correct option is D. A change will be observed in all three solutions because aluminium ( $Al$ ) is more reactive than copper ( $Cu$ ), iron ( $Fe$ ), and zinc ( $Zn$ ), allowing it to displace them from their respective sulphate solutions.

displacement reactionreactivity seriesAluminiummore reactivesulphate solutions

Marking Scheme

1Identification of the correct option D (1 mark)

Hint

Recall the reactivity series. A metal can only displace another metal from its salt solution if it is higher (more reactive) in the series. Compare the position of Aluminium with Copper, Iron, and Zinc.

Quick Oral Answer

Aluminium is more reactive than zinc, iron, and copper. Therefore, it can displace all three from their salt solutions. This is called a displacement reaction, and it results in observable changes like color shifts or metal deposition in all three test tubes.

Analysis & Explanation

This question is based on the principle of displacement reactions. A displacement reaction occurs when a more reactive element displaces a less reactive element from its compound. According to the reactivity series of metals, the order of reactivity is $Al > Zn > Fe > Cu$ .

In solution I ( $CuSO_4$ ), aluminium displaces copper:

$2Al(s) + 3CuSO_4(aq) \rightarrow Al_2(SO_4)_3(aq) + 3Cu(s)$

(Observation: Blue color fades, red-brown copper deposits).

In solution II ( $FeSO_4$ ), aluminium displaces iron:

$2Al(s) + 3FeSO_4(aq) \rightarrow Al_2(SO_4)_3(aq) + 3Fe(s)$

(Observation: Pale green color fades, grey iron deposits).

In solution III ( $ZnSO_4$ ), aluminium displaces zinc:

$2Al(s) + 3ZnSO_4(aq) \rightarrow Al_2(SO_4)_3(aq) + 3Zn(s)$

(Observation: Grey zinc deposits on the aluminium surface).

Since aluminium is more reactive than all three metals, a chemical reaction (and thus an observable change) occurs in every case.

Common Mistakes

1Thinking aluminium is less reactive than zinc because zinc is often discussed earlier in the chapter.
2Assuming no change occurs in zinc sulphate because the solution remains colorless.

Interesting Facts

Aluminium is highly reactive, but it often appears unreactive because it forms a very thin, tough layer of aluminium oxide ( $Al_2O_3$ ) on its surface when exposed to air.

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Frequently Asked Questions

How many marks does this question carry in CBSE Class 10 Science 2012?

This question carries 1 mark in the CBSE Class 10 Science 2012 examination.

Which chapter does this question come from in Science?

This question is from the chapter "Chemical Reactions and Equations" in the CBSE Class 10 Science syllabus.

What topic does this question cover in Science?

This question covers the topic "Types of Chemical Reactions" from CBSE Class 10 Science.

What type of question is this in the CBSE Class 10 Science 2012 paper?

This is a MCQ question from Section B in the CBSE Class 10 Science 2012 paper.