Q 11 :

Strong reducing and oxidizing agents among the following, respectively, are  [2023]

• ${\mathrm{Eu}}^{2+}$ and ${\mathrm{Ce}}^{4+}$

   

• ${\mathrm{Ce}}^{4+}$ and ${\mathrm{Eu}}^{2+}$

   

• ${\mathrm{Ce}}^{4+}$ and ${\mathrm{Tb}}^{4+}$

   

• ${\mathrm{Ce}}^{3+}$ and ${\mathrm{Ce}}^{4+}$

   

Q 12 :

Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R.

Assertion A: $5f$ electrons can participate in bonding to a far greater extent than $4f$ electrons.

Reason R: $5f$ orbitals are not as buried as $4f$ orbitals.

In the light of the above statements, choose the correct answer from the options given below.  [2023]

• Both A and R are true but R is not the correct explanation of A

   

• A is true but R is false

   

• A is false but R is true

   

• Both A and R are true and R is the correct explanation of A

   

Q 13 :

The pair of lanthanides in which both elements have high third-ionization energy is:  [2023]

• Dy, Gd

   

• Lu, Yb

   

• Eu, Yb

   

• Eu, Gd

   

Q 14 :

The incorrect statements among the following is               [2025]

• ${\mathrm{PH}}_3$ shows lower proton affinity than ${\mathrm{NH}}_3$.

   

• ${\mathrm{PF}}_3$ exists but ${\mathrm{NF}}_5$ does not.

   

• ${\mathrm{NO}}_2$ can dimerise easily.

   

• ${\mathrm{SO}}_2$ can act as an oxidizing agent, but not as a reducing agent.

   

Q 15 :

Given below are two statements:                                       [2025]

Statement I: The N—N single bond is weaker and longer than that of P—P single bond.

Statement II: Compounds of group 15 elements in +3 oxidation states readily undergo disproportionation reactions.

In the light of the above statements, choose the correct answer from the options given below:

• Statement I is true but Statement II is false.

   

• Both Statement I and Statement II are false.

   

• Both Statement I and Statement II are true.

   

• Statement I is false but Statement II is true.

   

Q 16 :

Consider the following reactions,

$A+\underset{\text{Little amount}}{\mathrm{NaCl}}+{\mathrm{H}}_2{\mathrm{SO}}_4\to {\mathrm{CrO}}_2{\mathrm{Cl}}_2+\text{Side products}$

${\mathrm{CrO}}_2{\mathrm{Cl}}_2\left(\text{Vapour}\right)+\mathrm{NaOH}⟶B+\mathrm{NaCl}+{\mathrm{H}}_2\mathrm{O}$

$B+{\mathrm{H}}^{+}⟶C+{\mathrm{H}}_2\mathrm{O}$

The number of terminal 'O' present in the compound 'C' is ________                   [2025]

Q 17 :

Consider the following reactions.

${\mathrm{PbCl}}_2+{\mathrm{K}}_2{\mathrm{CrO}}_4\to \mathrm{A}+2\mathrm{KCl}$

$\text{(Hot solution)}$

$\mathrm{A}+\mathrm{NaOH}\rightleftharpoons \mathrm{B}+{\mathrm{Na}}_2{\mathrm{CrO}}_4$

${\mathrm{PbSO}}_4+4{\mathrm{CH}}_3{\mathrm{COONH}}_4\to {\left({\mathrm{NH}}_4\right)}_2{\mathrm{SO}}_4+\mathrm{X}$

In the above reactions, A, B, and X are respectively.    [2026]

• ${\mathrm{Na}}_2\left[\mathrm{Pb}{\left(\mathrm{OH}\right)}_2\right],{\mathrm{PbCrO}}_4\text{ and }{\left({\mathrm{NH}}_4\right)}_2\left[\mathrm{Pb}{\left({\mathrm{CH}}_3\mathrm{COO}\right)}_4\right]$

   

• ${\mathrm{PbCrO}}_4,{\mathrm{Na}}_2\left[\mathrm{Pb}{\left(\mathrm{OH}\right)}_4\right]\text{ and }\left[\mathrm{Pb}{\left({\mathrm{NH}}_3\right)}_4\right]{\mathrm{SO}}_4$

   

• ${\mathrm{Na}}_2\left[\mathrm{Pb}{\left(\mathrm{OH}\right)}_2\right],{\mathrm{PbCrO}}_4\text{ and }\left[\mathrm{Pb}{\left({\mathrm{NH}}_3\right)}_4\right]{\mathrm{SO}}_4$

   

• ${\mathrm{PbCrO}}_4,{\mathrm{Na}}_2\left[\mathrm{Pb}{\left(\mathrm{OH}\right)}_4\right]\text{ and }{\left({\mathrm{NH}}_4\right)}_2\left[\mathrm{Pb}{\left({\mathrm{CH}}_3\mathrm{COO}\right)}_4\right]$

   

Q 18 :

X and Y are the number of electrons involved, respectively, during the oxidation of ${\mathrm{I}}^{-}$ to ${\mathrm{I}}_2$ and ${\mathrm{S}}^{2-}$ to $\mathrm{S}$ by acidified ${\mathrm{K}}_2{\mathrm{Cr}}_2{\mathrm{O}}_7$. The value of $\mathrm{X}+\mathrm{Y}$ is ____ .        [2026]

Q 19 :

Consider the following reactions $\mathrm{NaCl}+{\mathrm{K}}_2{\mathrm{Cr}}_2{\mathrm{O}}_7+{\mathrm{H}}_2{\mathrm{SO}}_4\to \mathrm{A}+{\mathrm{KHSO}}_4+{\mathrm{NaHSO}}_4+{\mathrm{H}}_2\mathrm{O}$ 

$\mathrm{A}+\mathrm{NaOH}\to \mathrm{B}+\mathrm{NaCl}+{\mathrm{H}}_2\mathrm{O}$

$\mathrm{B}+{\mathrm{H}}_2{\mathrm{SO}}_4+{\mathrm{H}}_2{\mathrm{O}}_2\to \mathrm{C}+{\mathrm{Na}}_2{\mathrm{SO}}_4+{\mathrm{H}}_2\mathrm{O}$

In the product `C',

`X' is the number of ${\mathrm{O}}_2^{2-}$ units,

`Y' is the total number oxygen atoms present and  

`Z' is the oxidation state of Cr. 

The value of X + Y + Z is ______.    [2026]

Q 20 :

Among the following oxides of 3d elements, the number of mixed oxides are ____________.

$Ti₂O₃, V₂O₄, Cr₂O₃, Mn₃O₄, Fe₃O₄, Fe₂O₃, Co₃O₄$        [2026]