1 Marks Question

Question 11 Mark

Which metal in the first series of transition metal exhibits +1 oxidation state most frequently and why?

Answer

Copper because it will achieve a completely filled $d$-orbital and a stable configuration on losing an electron.

Question 21 Mark

What is meant by 'disproportionation'? Give two examples of disproportionation reaction in aqueous solution.

Answer

(i) $MnO _4^{2-}+4 H ^{+} \longrightarrow 2 MnO _4^{-}+ MnO _2+2 H _2 O$,
(ii) $3 CrO _4^{3-}+8 H ^{+} \longrightarrow 2 CrO _4^{2-}+ Cr ^{3+}+4 H _2 O$.

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Question 31 Mark

Why are $Mn ^{2+}$ compounds more stable than $Fe ^{2+}$ towards oxidation to their +3 state?

Answer

$Mn ^{2+}$ has stable electronic configuration ([Ar] $4 s^0, 3 d^5$ ) and thus does not easily change to $Mn ^{3+} . Fe ^{2+}\left[[ Ar ] 4 s^0, 3 d^6\right]$ on oxidation forms $Fe ^{3+}$ [Ar] $4 s^0, 3 d^5$ ] a more stable configuration.

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Question 41 Mark

In what way is the electronic configuration of the transition elements different from that of the non-transition elements?

Answer

In transition elements, the penultimate shell is partially filled. In non-transition elements, first the inner shells are filled and then the last shell is filled.

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Question 51 Mark

Give reason and select one atom/ion which will exhibit asked property :
(i) $Sc ^{3+}{\text { or } Cr ^{3+}}^{3+}$ (Exhibit diamagnetic behaviour)
(ii) Cr or Cu (High melting and boiling point)

Answer

(i) $Sc ^{3+}$, because of absence of unpaired electron.
(ii) Cr, because of presence of stronger intermetallic bonding than Cu .

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Question 61 Mark

When $MnO _2$ is fused with KOH in presence of $KNO _3$ as an oxidizing agent, it gives a dark green compound (A). Compound (A) disproportionate in acidic solution to give purple compound (B). An alkaline solution of compound (B) oxidises KI to compound (C) whereas an acidified solution of compound (B) oxidises KI to (D). Identify (A), (B), (C) and (D).

Answer

(A) $K _2 MnO _4$ green, (B) $KMnO _4$ purple, (C) $Mn _2 O _3$, (D) $Mn _2 O _4$.

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Question 71 Mark

Complete and balance the following chemical equations :
(i) $F e ^{ 2 + }+ M n O _4^{-}+ H ^{+} \rightarrow$
(ii) $MnO _4^{-}+ H _2 O + I ^{-} \rightarrow$

Answer

(i) $5 Fe ^{2+}+ MnO _4^{-}+8 H ^{+} \rightarrow Mn ^{2+}+4 H _2 O +5 Fe ^{3+}$
(ii) $2 MnO _4^{-}+ H _2 O + I ^{-} \rightarrow 2 MnO ^2+2 OH ^{-}+ IO _3^{-}$

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Question 81 Mark

Write electronic configuration of the following elements:
(i) V (Z=23)
(ii) Zn (Z=30)

Answer

(i) ${ }_{23} V \longrightarrow 1 s^2, 2 s^2 2 p^6, 3 s^2 3 p^6 3 d^3, 4 s^2$
(ii) $30 Zn \longrightarrow 1 s^2, 2 s^2 2 p^6, 3 s^2 3 p^6 3 d^{10}, 4 s^2$

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Question 91 Mark

Why is separation of lanthanoid elements difficult?

Answer

The separation of lanthanoid elements is difficult because of lanthanoid contraction. Due to contraction the change in atomic and ionic radii is very small and these elements show similar chemical properties and the separation becomes difficult.

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Question 101 Mark

What are interstitial compounds? Why are such compounds well known for transition metals?

Answer

Interstitial compounds are formed when small non-metallic atoms like H and C are trapped inside the crystal lattice of metals.

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Question 111 Mark

Why is $ Cu^{+} $ diamagnetic whereas $ Cu^{2+} $ is paramagnetic?

Answer

$ Cu^{+} $ has configuration [Ar] $ 3d^{10} $ whereas $ Cu^{2+} $ has [Ar] $ 3d^{9} $. It is thus evident that $ Cu^{+} $ has no unpaired electron and thus diamagnetic. $ Cu^{2+} $ has one unpaired electron in 3d sub-shell and thus paramagnetic.

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Question 121 Mark

What are transition metals? Which d-block elements are not normally considered as transition metals?

Answer

Transition metals are those elements which have incomplete d-orbital and the last electron enters the (n-1)d orbital. Zn, Cd, Hg are not consider as transition metals.

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Question 131 Mark

Explain why iron (Fe) is a transition metal, but sodium is not?

Answer

Iron is a d-block element and shows properties of transition metals like variable valancy, coloured ion, complex formation etc. Sodium is a s-block element. It does not show the properties of transition metal.

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Question 141 Mark

Explain giving reason:
(a) Transition metals and many of their compounds show paramagnetic behaviour.
(b) The enthalpies of atomisation of the transition metals are high.
(c) Transition metals in their many compounds act as good catalyst.

Answer

(a) Due to the presence of unpaired electrons.
(b) Due to strong inter-atomic forces.
(c) Due to variable oxidation states.

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Question 151 Mark

Any transition series contains only ten elements, why?

Answer

It is because there are only 10 members since in the period left to right atomic number increases and hence after a certain number when the d subshell is fully filled the electron has to go in the s and p-subshell and hence it (d-block) ends up with only 10 elements.

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Chemistry 1 Marks Question

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