SECTION - B [CHEMISTY - NUMERIC] - JEE STD 11 Science Questions

Question 14 Marks

Total number of molecules/species from following which will be paramagnetic is _______________ .
$\mathrm{O}_{2}, \mathrm{O}_{2}^{+}, \mathrm{O}_{2}^{-}, \mathrm{NO}, \mathrm{NO}_{2}, \mathrm{CO}, \mathrm{K}_{2}\left[\mathrm{NiCl}_{4}\right]$,
$\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{6}\right] \mathrm{Cl}_{3}, \mathrm{~K}_{2}\left[\mathrm{Ni}(\mathrm{CN})_{4}\right]$

Answer

6
$\mathrm{O}_{2} \rightarrow 2$ unpaired electrons according to MOT
$\mathrm{O}_{2}{ }^{+} \rightarrow 1$ unpaired electrons according to MOT
$\mathrm{O}_{2}^{-} \rightarrow 1$ unpaired electrons according to MOT
NO $\rightarrow$ odd electron species
$\mathrm{NO}_{2} \rightarrow$ odd electron species
$\mathrm{K}_{2}\left[\mathrm{NiCl}_{4}\right] \rightarrow \mathrm{Ni}^{2+} \Rightarrow 3 \mathrm{~d}^{8}$ weak Ligand, C.N. $=4$
$\Rightarrow$ Tetrahedral, Paramagnetic with 2 unpaired electrons

View full question & answer→

Question 24 Marks

A group 15 element forms $\mathrm{d} \pi-\mathrm{d} \pi$ bond with transition metals. It also forms hydride, which is a strongest base among the hydrides of other group members that form $\mathrm{d} \pi-\mathrm{d} \pi$ bond. The atomic number of the element is _______________ .

Answer

15
Phosphorus belongs to $15^{\text {th }}$ group and forms $\mathrm{d} \pi-\mathrm{d} \pi$ bond with transition metal and $\mathrm{PH}_{3}$ is strongest base among the other group members excepet $\mathrm{NH}_{3}$.

View full question & answer→

Question 34 Marks

Electrolysis of 600 mL aqueous solution of NaCl for 5 min changes the pH of the solution to 12 .
The current in Amperes used for the given electrolysis is _______________ . (Nearest integer).

Answer

2
Electrolysis of NaCl is
$\mathrm{NaCl}+\mathrm{H}_{2} \mathrm{O}(\mathrm{aq}) \rightarrow \mathrm{NaOH}(\mathrm{aq})+\frac{1}{2} \mathrm{Cl}_{2}(\mathrm{~g})+\frac{1}{2} \mathrm{H}_{2}(\mathrm{~g})$
Since during electrolysis pH changes to 12
So $\left[\mathrm{OH}^{\ominus}\right]=10^{-2}$ and $\left[\mathrm{H}^{+}\right]=10^{-12}$
So by Faraday law
Gram amount of substance deposited $=$Amount of electricity passed
$10^{-2} \times \frac{600}{1000} \times 96500=\mathrm{I} \times \mathrm{t}$
$\frac{10^{-2} \times 600}{1000} \times 96500=\mathrm{I} \times 5 \times 60$
$I=\frac{10^{-2} \times 600 \times 96500}{1000 \times 5 \times 60}$
$\mathrm{I}=1.93$ ampere
So, I = 2 ampere (nearest integer)

View full question & answer→

Question 44 Marks

Consider the following data :
Heat of formation of $\mathrm{CO}_{2}(\mathrm{~g})=-393.5 \mathrm{~kJ} \mathrm{~mol}^{-1}$
Heat of formation of $\mathrm{H}_{2} \mathrm{O}(\mathrm{l})=-286.0 \mathrm{~kJ} \mathrm{~mol}^{-1}$
Heat of combustion of benzene $=-3267.0 \mathrm{~kJ} \mathrm{~mol}^{-1}$
The heat of formation of benzene is _______________ $\mathrm{kJ} \mathrm{mol}^{-1}$.
(Nearest integer)

Answer

48.
$ \Delta \mathrm{H}_{\mathrm{f}}\left[\mathrm{CO}_{2}(\mathrm{~g})\right]=-393.5 \mathrm{~kJ} /$ mole
$\Delta \mathrm{H}_{\mathrm{f}}\left[\mathrm{H}_{2}\mathrm{O}(\ell)\right]=-286.0 \mathrm{~kJ} /$ mole
$\Delta \mathrm{H}_{\mathrm{c}}\left[\mathrm{C}_{6} \mathrm{H}_{6}\right]=-3267.0 \mathrm{~kJ} / \mathrm{mole}$
$\Delta \mathrm{H}_{\mathrm{f}} \mathrm{C}_{6} \mathrm{H}_{6}=(?)$
$\mathrm{C}_{6} \mathrm{H}_{6}+\frac{15}{2} \mathrm{O}_{2}(\mathrm{~g}) \longrightarrow 6 \mathrm{CO}_{2}(\mathrm{~g})+3 \mathrm{H}_{2} \mathrm{O}(\ell)$
$\Delta \mathrm{H}_{\mathrm{R}}=\Delta \mathrm{H}_{\mathrm{C}}=\Sigma \Delta \mathrm{H}_{\mathrm{f}}(\mathrm{P})-\Sigma \Delta \mathrm{H}_{\mathrm{f}}(\mathrm{R})$
$-3267=6 \times(-393.5)+3(-286)-\Delta \mathrm{H}_{\mathrm{f}}\left(\mathrm{C}_{6} \mathrm{H}_{6}\right)$
$\Delta \mathrm{H}_{\mathrm{f}}\left(\mathrm{C}_{6} \mathrm{H}_{6}\right)=48 \mathrm{~kJ} / \mathrm{mole}$

View full question & answer→

Question 54 Marks

The spin only magnetic moment ( $\mu$ ) value (B.M.) of the compound with strongest oxidising power among $\mathrm{Mn}_{2} \mathrm{O}_{3}$, TiO and VO is _______________ B.M.
(Nearest integer).

Answer

5.
Strongest oxidising power among the option is
$\mathrm{Mn}_{2} \mathrm{O}_{3}$ because of $\mathrm{E}^{\circ}$ value
$\mathrm{E}_{\mathrm{Mn}^{+3} / \mathrm{Mn}^{+2}}^{\circ}=+1.57 \mathrm{~V}$
$\mathrm{Mn}^{+3} \rightarrow \mathrm{~d}^{4}$ configuration
$\mu=\sqrt{24} \mathrm{BM}$
$=4.89 \mathrm{BM}$
$\Rightarrow 5$

View full question & answer→

JEE SECTION - B [CHEMISTY - NUMERIC]

SECTION - B [CHEMISTY - NUMERIC]

Take a timed test