Physical Chemistry PYQ — Page 43

Which one of the following $0.10M$ aqueous solutions will exhibit the largest freezing point depression?

If $80g$ of copper sulphate ${\mathrm{CuSO}}_{4}\cdot 5{H}_{2}O$ is dissolved in deionised water to make $5L$ of solution. The concentration of the copper sulphate solution is $x\times {10}^{-3}\text{ mol }{L}^{-1}.$ The value of $x$ is _____. $[\text{Atomic masses }\mathrm{Cu}:63.54u,S:32u,O:16u,H:1u]$

$40g$ of glucose (Molar mass $=180)$ is mixed with $200\mathrm{mL}$ of water. The freezing point of solution is $__K$. (Nearest integer) [Given : ${K}_{f}=1.86K\mathrm{kg}{\mathrm{mol}}^{-1};$ Density of water $=1.00g{\mathrm{cm}}^{-3};$ Freezing point of water $=273.15K]$

A solute $A$ dimerizes in water. The boiling point of a $2$ molal solution of $A$ is $100.52C\circ$. The percentage association of $A$ is ___ . (Round off to the Nearest integer) Use : ${K}_{b}$ for water $=0.52K\mathrm{kg}{\mathrm{mol}}^{-1}$ Boiling point of water $=100^{\circ}C$

If a compound $\mathrm{AB}$ dissociates to the extent of $75%$ in an aqueous solution, the molality of the solution which shows a $2.5K$ rise in the boiling point of the solution is ___ molal. (Rounded-off to the nearest integer) $[{K}_{b}=0.52K\mathrm{kg}{\mathrm{mol}}^{-1}]$.

${\mathrm{AB}}_{2}$ is $10%$ dissociated in water to ${A}^{2+}$ and ${B}^{-}$. The boiling point of $10.0$ molal aqueous solution of ${\mathrm{AB}}_{2}$ is-- $C\circ$. (Round off to the Nearest Integer). [Given : Molal elevation constant of water ${K}_{b}=0.5K\mathrm{kg}{\mathrm{mol}}^{-1}$ boiling point of pure water$=100^{\circ}C$]

A solution is $0.1M$ in ${\mathrm{Cl}}^{-}$ and $0.001M$ in ${\mathrm{CrO}}_{4}^{2-}.$ Solid ${\mathrm{AgNO}}_{3}$ is gradually added to it Assuming that the addition does not change in volume and ${K}_{\mathrm{sp}}(\mathrm{AgCl})=1.7\times {10}^{-10}{M}^{2}$ and ${K}_{\mathrm{sp}}({\mathrm{Ag}}_{2}{\mathrm{CrO}}_{4})=1.9\times {10}^{-12}{M}^{3}.$ Select correct statement from the following:

For the galvanic cell, $\mathrm{Zn}(s)+{\mathrm{Cu}}^{2+}(0.02M)\rightarrow {\mathrm{Zn}}^{2+}(0.04M)+\mathrm{Cu}(s)$ ${E}_{\mathrm{cell}}=\ldots \times {10}^{-2}V$ (Nearest integer) $[\mathrm{Use}:{E}^{0}\mathrm{Cu}/{\mathrm{Cu}}^{2+}=-0.34V,{E}_{\mathrm{Zn}/{\mathrm{Zn}}^{2}+}=+0.76V,\frac{2.303\mathrm{RT}}{F}=0.059V]$

A $\mathrm{KCl}$ solution of conductivity $0.14S{m}^{-1}$ shows a resistance of $4.19\Omega$ in a conductivity cell. If the same cell is filled with an $\mathrm{HCl}$ solution, the resistance drops to $1.03\Omega$. The conductivity of the HCl solution is ____$\times {10}^{-2}S{m}^{-1}$. (Round off to the Nearest Integer).

The magnitude of the change in oxidising power of the ${\mathrm{MnO}}_{4}^{-}/{\mathrm{Mn}}^{2+}$ couple is $x\times {10}^{-4}V$ if the ${H}^{+}$ concentration is decreased from $1M$ to ${10}^{-4}M$ at $25^{\circ}C.$ (Assume concentration of ${\mathrm{MnO}}_{4}^{-}$ and ${\mathrm{Mn}}^{2+}$ to be same on change in ${H}^{+}$ concentration). The value of $x$ is __________. (Rounded off to the nearest integer) [Given: $\frac{2.303\mathrm{RT}}{F}=0.059$]

The Azimuthal quantum number for the valence electrons of ${\mathrm{Ga}}^{+}$ ion is (Atomic number of $\mathrm{Ga}=31$)

 Consider the above reaction. The percentage yield of amide product is (Round off to the Nearest Integer). (Given : Atomic mass : $C:12.0u,H:1.0u$ $N:14.0u,O:16.0u,\mathrm{Cl}:35.5u)$

An accelerated electron has a speed of $5\times {10}^{6}{\mathrm{ms}}^{-1}$ with an uncertainty of $0.02%$. The uncertainty in finding its location while in motion is $x\times {10}^{-9}m$. The value of $x$ is __________. (Nearest integer) [Use mass of electron$=9.1\times {10}^{-31}\mathrm{kg}$, $h=6.63\times {10}^{-34}\mathrm{Js},\pi =3.14]$

At $298.2K$ the relationship between enthalpy of bond dissociation (in $\mathrm{kJ}{\mathrm{mol}}^{-1}$) for hydrogen $({E}_{H})$ and its isotope, deuterium $({E}_{D})$, is best described by:

The vapour pressures of $A$ and $B$ at $25^{\circ}C$ are $90\mathrm{mmHg}$ and $15\mathrm{mm}\mathrm{Hg}$ respectively. If $A$ and $B$ are mixed such that the mole fraction of $A$ in the mixture is $0.6,$ then the mole fraction of $B$ in the vapour phase is $x\times {10}^{-1}.$ The value of $x$ is (Nearest integer)

Given below are two statements : Statement I : The $E^{\circ}$ value of ${\mathrm{Ce}}^{4+}/{\mathrm{Ce}}^{3+}$ is $+1.74V$ Statement II : Ce is more stable in ${\mathrm{Ce}}^{4+}$ state than ${\mathrm{Ce}}^{3+}$ state. In the light of the above statements, choose the most appropriate answer from the options given below:

The rate constant of a reaction increases by five times on increase in temperature from $27^{\circ}C$ to $52^{\circ}C$. The value of activation energy in ${\mathrm{kJmol}}^{-1}$ is ___ .(Rounded-off to the nearest integer) $[R=8.314J{K}^{-1}{\mathrm{mol}}^{-1}]$

$10.0\mathrm{mL}$ of $0.05M{\mathrm{KMnO}}_{4}$ solution was consumed in a titration with $10.0\mathrm{mL}$ of given oxalic acid dihydrate solution. The strength of given oxalic acid solution is ........ $\times {10}^{-2}g/L$. (Round off to the nearest integer)

 In the above reaction, $3.9g$ of benzene on nitration gives $4.92g$ of nitrobenzene. The percentage yield of nitrobenzene in the above reaction is _________ $%$. (Round off to the Nearest Integer). (Given atomic mass : $C:12.0u,H:1.0u$$O:16.0u,N:14.0u$)

The solubility of $\mathrm{Ca}{(\mathrm{OH})}_{2}$ in water is : [Given : The solubility product of $\mathrm{Ca}{(\mathrm{OH})}_{2}$ in water $=5.5\times {10}^{-6}$]

Copper reduces ${\mathrm{NO}}_{3}^{-}$ into $\mathrm{NO}$ and ${\mathrm{NO}}_{2}$ depending upon the concentration of ${\mathrm{HNO}}_{3}$ in solution. (Assuming fixed $[{\mathrm{Cu}}^{2+}]$ and ${P}_{\mathrm{NO}}={P}_{{\mathrm{NO}}_{2}}$), the ${\mathrm{HNO}}_{3}$ concentration at which the thermodynamic tendency for reduction of ${\mathrm{NO}}_{3}^{-}$ into $\mathrm{NO}$ and ${\mathrm{NO}}_{2}$ by copper is same is ${10}^{x}M$. The value of $2x$ is ___. (Rounded-off to the nearest integer) [Given, ${E}_{{\mathrm{Cu}}^{2+}/\mathrm{Cu}}^{o}=0.34V,{E}_{{\mathrm{NO}}_{3}^{-}/\mathrm{NO}}^{o}=0.96V,{E}_{{\mathrm{NO}}_{3}^{-}/{\mathrm{NO}}_{2}}^{o}=0.79V$ and at $298K$, $\frac{\mathrm{RT}}{F}(2.303)=0.059$]

The gas phase reaction $2A(g)\rightleftharpoons {A}_{2}(g)$ at $400K$ has $\Delta {G}^{o}=+25.2\mathrm{kJ}{\mathrm{mol}}^{-1}$. The equilibrium constant ${K}_{C}$ for this reaction is ___ $\times {10}^{-2}$. (Round off to the Nearest integer) Use : $R=8.3J{\mathrm{mol}}^{-1}{K}^{-1},\mathrm{ln}10=2.3 {\mathrm{log}}_{10}2=0.30,1\mathrm{atm}=1\mathrm{bar}$ antilog $(-0.3)=0.501$

For water at $100^{\circ}C$ and $1$ bar, ${\Delta }_{vap}H-{\Delta }_{vap}U=\underset{¯}{}\times {10}^{2}J{\mathrm{mol}}^{-1}$ (Round off to the Nearest Integer) [Use : $R=8.31J{\mathrm{mol}}^{-1}{K}^{-1}]$ [Assume volume of ${H}_{2}O(l)$ is much smaller than volume of ${H}_{2}O(g)$. Assume ${H}_{2}O(g)$ treated as an ideal gas]

During which of the following processes, does entropy decrease ? (A) Freezing of water to ice at $0^{\circ}C$ (B) Freezing of water to ice at $-10^{\circ}C$ (C) ${N}_{2}(g)+3{H}_{2}(g)\rightarrow 2{\mathrm{NH}}_{3}(g)$ (D) Adsorption of $\mathrm{CO}(g)$ and lead surface (E) Dissolution of $\mathrm{NaCl}$ in water