Answer the questions.[Che-3M]

Question 13 Marks

Sample pieces of five metals A, B, C, D and E were added to the tabulated solutions separately. The results observed are shown in the table:

Metal	FeSO₄	CuSO₄	ZnSO₄	A_gNO₃	Al₂(SO₄)₃
A	No Change	No Change	No Change	Coating on metal	No Change
B	Grey Deposit on metal	Brown Coating on metal	No Change	Coating on metal	No Change
C	No Change	No Change	No Change	No Change	No Change
D	No Change	---------	No Change	Coating on metal	No Change
E	---------	Brown Coating	New Coating	New Coating	No Change

Based on the observations recorded in the table, answer the following:
(1) Which is the most reactive metal?
(2) Which is the least reactive metal?
(3) What would be observed if metal D were added to a solution of copper (II) sulphate?
(4) What would be observed if metal E were added to a solution of iron (II) sulphate?
(5) Arrange the metals $\mathrm{A}, \mathrm{B}, \mathrm{C}, \mathrm{D}$ and E in decreasing order of their reactivity?

Answer

(1) Metal E is most reactive because it displaces zinc from $\mathrm{ZnSO}_{4}$ solution.
(2) Metal C is the least reactive since it has not displaced any of the metals from their respective salt solutions.
(3) Metal D is more reactive than Ag and less reactive than Fe . It can displace Cu from $\mathrm{CuSO}_{4}$ solution.
(4) Since metal E has displaced Zn from $\mathrm{ZnSO}_{4}$ solution, it is more reactive than Zinc . It is therefore expected to be more reactive than iron as well because iron is placed below zinc in the reactive series. Therefore, metal E displaces Fe from $\mathrm{FeSO}_{4}$ solution. A grey /black coating of iron will be deposited on the metal E.
(5) Decreasing order of reactivity $\mathrm{E}>\mathrm{B}>\mathrm{D}>\mathrm{A}>\mathrm{C}$

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Question 23 Marks

Translate the following statement into a chemical equation and then balance it :
Barium chloride reacts with aluminium sulphate to give aluminium chloride and a precipitate of barium sulphate.

Answer

Barium chloride reacts with aluminium sulphate to give aluminium and separates Barium sulfate( $\mathrm{BaSO}_{4}$ ).
$3 \mathrm{BaCl}_{2}(\mathrm{aq})+\mathrm{Al}_{2}\left(\mathrm{SO}_{4}\right)_{3}(\mathrm{aq}) \rightarrow 2 \mathrm{AlCl}_{3}(\mathrm{aq})+3 \mathrm{BaSO}_{4}(\mathrm{~s}) \downarrow$

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Question 33 Marks

What is a displacement reaction? Write balanced chemical equation for a displacement reaction in which iron is a reactant. Name one more element whose behaviour is similar to that of iron in such reactions. Why will this kind of behaviour not be shown by gold?

Answer

Displacement reaction is a type of reaction in which a more reactive element displaces another less reactive element. The reactivity series of metals can be used to find out the displacement reaction.
Chemical equation for a displacement reaction in which Iron is a reactant:
$\mathrm{Fe}+\mathrm{CuSO}_{4} \rightarrow \mathrm{FeSO}_{4}+\mathrm{Cu}$
One more element whose behaviour is similar to that of iron in such reaction is Zn .
$\mathrm{Zn}+2 \mathrm{HCl} \rightarrow \mathrm{ZnCl}_{2}+\mathrm{H}_{2} \uparrow$
This is not shown by Gold as it is the least reactive element.

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