d and f Block Elements — Page 19 | JEE Chemistry

Q181

What is the spin-only magnetic moment value (BM) of a divalent metal ion with atomic number 25, in it's aqueous solution?

A zero

B 5.26

C 5.0

D 5.92

Correct Answer

Option D

Solution

25Mn = [Ar]3d5 4s2 Mn2+ = [Ar]3d5 4s0 No. of unpaired electron (n) = 5

\mu = \sqrt {n\left( {n + 2} \right)} \,BM

= \sqrt {5 \times 7} {\rm{ }} = \sqrt {35} {\rm{ }} = {\rm{ }}5.92{\rm{ }}

BM

Q182

Given below are two statements : Statement I : Potassium permanganate on heating at 573K forms potassium manganate. Statement II : Both potassium permanganate and potassium manganate are tetrahedral and paramagnetic in nature. In the light of the above statements, choose the most appropriate answer from the options given below :

A Statement I is true but statement II is false

B Statement I is false but statement II is true

C Both statement I and statement II are false

D Both statement I and statement II are true

Correct Answer

Option A

Solution

Statement-1 : KMnO4

\overset{{573K}}\longrightarrow

K2MnO4 + MnO2 + O2 Statement-2 : KMnO4 $\Rightarrow$ Mn7+ $\Rightarrow$ Diamagnetic.

KMnO4 $\Rightarrow$ Mn6+ $\Rightarrow$ Paramagnetic.

Q183

The set having ions which are coloured and paramagnetic both is :

A Cu2+, Cr3+, Sc+

B Cu2+, Zn2+, Mn4+

C Sc3+, V5+, Ti4+

D Ni2+, Mn7+, Hg2+

Correct Answer

Option A

Solution

\left. \begin{array}{ll}C{u^{2 + }}:[Ar]3{d^9}4{s^0} \\ C{r^{3 + }}:[Ar]3{d^3}4{s^0} \\ S{c^ + }:[Ar]3{d^1}4{s^1} \end{array} \right]

All are coloured and paramagnetic due to presence of unpaired electrons

Q184

Which one of the following when dissolved in water gives coloured solution in nitrogen atmosphere?

A CuCl2

B AgCl

C ZnCl2

D Cu2Cl2

Correct Answer

Option A

Solution

(a) CuCl2 + nH2O $\to$ Cu

_{(aq.)}^{ + 2}

(blue colour) (b) AgCl + nH2O $\to$ Insoluble (c) ZnCl2 + nH2O $\to$ Zn

_{(aq.)}^{ + 2}

Colourless (d) Cu2Cl2 + nH2O $\to$ Insoluble

Q185

The nature of oxides V2O3 and CrO is indexed as 'X' and 'Y' type respectively. The correct set of X and Y is :

A X = basic Y = amphoteric

B X = amphoteric Y = basic

C X = acidic Y = acidic

D X = basic Y = basic

Correct Answer

Option D

Solution

V2O3 basic CrO basic

Q186

The addition of dilute NaOH to Cr3+ salt solution will give :

A a solution of [Cr(OH)4]

-

B precipitate of Cr2O3(H2O)n

C precipitate of [Cr(OH)6]3

-

D precipitate of Cr(OH)3

Correct Answer

Option B

Solution

C{r^{3 + }} + \mathop {NaOH}\limits_{dil.} \overset{{}}\longrightarrow \mathop {C{r_2}{O_3}.{{({H_2}O)}_n}}\limits_{precipitate}

Q187

Potassium permanganate on heating at 513 K gives a product which is :

A paramagnetic and colourless

B diamagnetic and green

C diamagnetic and colourless

D paramagnetic and green

Correct Answer

Option D

Solution

2KMn{O_4}\mathrel{\mathop{\kern0pt\longrightarrow} \limits_{200^\circ C}^\Delta } \mathop {{K_2}Mn{O_4}}\limits_{Green} + \mathop {Mn{O_2}}\limits_{Black} + {O_2}

In K2MnO4, manganese oxidation state is +6 and hence it has one unpaired e $-$ .

Q188

The most common oxidation state of Lanthanoid elements is +3. Which of the following is likely to deviate easily from +3 oxidation state?

A Ce (At. No. 58)

B La (At. No. 57)

C Lu (At. No. 71)

D Gd (At. No. 64)

Correct Answer

Option A

Solution

Ce → [Xe]4f1 5d1 6s2 Ce+4 → [xe] 4f° 5d° 6s° Cerium in +4 oxidation state acquires inert gas configuration.

Q189

Among the following, which is the strongest oxidizing agent?

A Mn3+

B Fe3+

C Ti3+

D Cr3+

Correct Answer

Option A

Solution

Strongest oxidising agent have highest reduction potential value

\mathrm{E}_{\mathrm{Fe}^{3+} \mid \mathrm{Fe}^{2+}}^{\circ}= + 0.77 \mathrm{~V} \quad \mathrm{E}_{\mathrm{Ti}^{3+} \mid \mathrm{Ti}^{2+}}^{\circ}=-0.37 \mathrm{~V}

\mathrm{E}^{\circ}_{\mathrm{Mn}^{+3} \mid \mathrm{Mn}^{+2}}=+1.57 \mathrm{~V} \quad \mathrm{E}^{\circ}_{\mathrm{Cr}^{3+}\mid\mathrm{Cr}^{2+}} = -0.41 \mathrm{~V}

\mathrm{Mn}^{+3}

is the best oxidising agent among the given series.

Q190

Metals generally melt at very high temperature. Amongst the following, the metal with the highest melting point will be :

A Hg

B Ag

C Ga

D Cs

Correct Answer

Option B

Solution

Melting points of the given metals Hg : –38.83° C Ag : 961.8° C Ga : 29.76° C Cs : 28.44° C $\therefore$ Metal having highest melting point is Ag.