Physical Chemistry PYQ — Page 29

An aqueous solution of volume $300{\mathrm{cm}}^{3}$ contains $0.63g$ of protein. The osmotic pressure of the solution at $300K$ is $1.29\mathrm{mbar}$. The molar mass of the protein is ${\mathrm{gmol}}^{-1}$. Given : $R=0.083{L}_{\mathrm{bar}}{K}^{-1}{\mathrm{mol}}^{-1}$

Evaluate the following statements for their correctness. A. The elevation in boiling point temperature of water will be same for $0.1M$ $\mathrm{NaCl}$ and $0.1M$ urea. B. Azeotropic mixture boil without change in their composition. C. Osmosis always takes place from hypertonic to hypotonic solution. D. The density of $32%$ ${H}_{2}{\mathrm{SO}}_{4}$ solution having molarity $4.09M$ is approximately $1.26g{\mathrm{mL}}^{–1}$. E. A negatively charged sol is obtained when $\mathrm{KI}$ solution is added to silver nitrate solution. Choose the correct answer from the options given below:

Consider the following reaction approaching equilibrium at $27^{\circ}C$ and $1$ atm pressure $A+B\underset{{K}_{r}={10}^{2}}{\overset{{K}_{t}={0}^{3}}{\rightleftharpoons }}C+D$ The standard Gibb's energy change $({\Delta }_{r}G^{\circ})$ at $27^{\circ}C$ is $(-)$ _____ ${\mathrm{kJmol}}^{-1}$ (Nearest integer). (Given : $R=8.3J{K}^{-1}{\mathrm{mol}}^{-1}$ and $\mathrm{ln}10=2.3$)

At equilibrium, the rate of forward reaction is

Mass of Urea $({\mathrm{NH}}_{2}{\mathrm{CONH}}_{2})$ required to be dissolved in $1000g$ of water in order to reduce the vapour pressure of water by $25%$ is $_______g.$ (Nearest integer) Given : Molar mass of $N,C,O$ and $H$ are $14,12,16$ and $1g{\mathrm{mol}}^{-1}$ respectively.

${t}_{87.5}$ is the time required for the reaction to undergo $87.5%$ completion and ${t}_{50}$ is the time required for the reaction to undergo $50%$ completion. The relation between ${t}_{87.5}$ and ${t}_{50}$ for a first order reaction is ${t}_{87.5}=x\times {t}_{50}$ The value of $x$ is $_________.$ (Nearest integer)

A mixture of one mole of ${H}_{2}O$ and 1 mole of $\mathrm{CO}$ is taken in a $10\mathrm{litre}$ container and heated to $725K$. At equilibrium $40%$ of water by mass reacts with carbon monoxide according to the equation: $\mathrm{CO}(g)+{H}_{2}O(g)\overset{}{\rightleftharpoons }{\mathrm{CO}}_{2}(g)+{H}_{2}(g)$. The equilibrium constant ${K}_{C}\times {10}^{2}$ for the reaction is ________ (Nearest integer)

Given below are two statements : one is labelled as Assertion A and the other is labelled as Reason R : Assertion A: In the photoelectric effect, the electrons are ejected from the metal surface as soon as the beam of light of frequency greater than threshold frequency strikes the surface. Reason R : When the photon of any energy strikes an electron in the atom, transfer of energy from the photon to the electron takes place. In the light of the above statements, choose the most appropriate answer from the options given below :

For complete combustion of ethene, ${C}_{2}{H}_{4}(g)+3{O}_{2}(g)\rightarrow 2{\mathrm{CO}}_{2}(g)+2{H}_{2}O(l)$ the amount of heat produced as measured in bomb calorimeter is $1406\mathrm{kJ}{\mathrm{mol}}^{-1}$ at $300K$. The minimum value of $T\Delta S$ needed to reach equilibrium is $(-)$ $\mathrm{kJ}$. (Nearest integer) Given: $R=8.3J{K}^{-1}{\mathrm{mol}}^{-1}$

$20\mathrm{mL}$ of calcium hydroxide was consumed when it was reacted with $10\mathrm{mL}$ of unknown solution of ${H}_{2}{\mathrm{SO}}_{4}.$ Also $20\mathrm{mL}$ standard solution of $0.5M\mathrm{HCl}$ containing $2$ drops of phenolphthalein was titrated with calcium hydroxide, the mixture showed pink colour when burette displayed the value of $35.5\mathrm{mL}$ whereas the burette showed $25.5\mathrm{mL}$ initially. The concentration of ${H}_{2}{\mathrm{SO}}_{4}$ is $_______M.$ (Nearest integer)

Sea water contains $29.25%\mathrm{NaCl}$ and $19%{\mathrm{MgCl}}_{2}$ by weight of solution. The normal boiling point of the sea water is $C\circ$ (Nearest integer) Assume $100%$ ionization for both $\mathrm{NaCl}$ and ${\mathrm{MgCl}}_{2}$ Given: ${K}_{b}({H}_{2}O=0.52K\mathrm{kg}{\mathrm{mol}}^{-1})$ Molar mass of $\mathrm{NaCl}$ and ${\mathrm{MgCl}}_{2}$ is $58.5$ and $95g$ ${\mathrm{mol}}^{-1}$ respectively.

The resistivity of a $0.8M$ solution of an electrolyte is $5\times {10}^{-3}\Omega cm$. Its molar conductivity is ${10}^{4}{\Omega }^{-1}{\mathrm{cm}}^{2}{\mathrm{mol}}^{-1}$. (Nearest integer)

Consider the cell ${\mathrm{Pt}}_{(s)}|{H}_{2}(g,1\mathrm{atm})|{H}^{+}(\mathrm{aq},1M)||{\mathrm{Fe}}^{3+}(\mathrm{aq}),{\mathrm{Fe}}^{2+}(\mathrm{aq})|Pt(s)$ When the potential of the cell is $0.712V$ at $298K$, the ratio $[{\mathrm{Fe}}^{2+}]/[{\mathrm{Fe}}^{3+}]$ is (Nearest integer) Given: ${\mathrm{Fe}}^{3+}+{e}^{-}={\mathrm{Fe}}^{2+},E^{\circ}{\mathrm{Fe}}^{3+},{\mathrm{Fe}}^{2+}\mathrm{Pt}=0.771\frac{2.303\mathrm{RT}}{F}=0.06V$

The reaction $2\mathrm{NO}+{\mathrm{Br}}_{2}\rightarrow 2\mathrm{NOBr}$ takes place through the mechanism given below $\mathrm{NO}+{\mathrm{Br}}_{2}\overset{}{\rightleftharpoons }{\mathrm{NOBr}}_{2}(\mathrm{fast})$ ${\mathrm{NOBr}}_{2}+\mathrm{NO}\rightarrow 2\mathrm{NOBr}(\mathrm{slow})$ The overall order of the reaction is _____.

$25.0\mathrm{mL}$ of $0.050M\mathrm{Ba}{({\mathrm{NO}}_{3})}_{2}$ is mixed with $25.0\mathrm{mL}$ of $0.020M\mathrm{NaF}.{K}_{\mathrm{sp}}$ of ${\mathrm{BaF}}_{2}$ is $0.5\times 10–6$ at $298K.$ The ratio of $[{\mathrm{Ba}}^{2+}]{[{F}^{-}]}^{2}$ and ${K}_{\mathrm{sp}}$ is $______.$

When a $60W$ electric heater is immersed in a gas for $100s$ in a constant volume container with adiabatic walls, the temperature of the gas rises by $5^{\circ}C$. The heat capacity of the given gas is ${\mathrm{JK}}^{-1}$ (Nearest integer)

$A\rightarrow B$ The above reaction is of zero order. Half life of this reaction is $50\mathrm{min}$. The time taken for the concentration of $A$ to reduce to one-fourth of its initial value is min . (Nearest integer)

(i) $X(g)\rightleftharpoons Y(g)+Z(g){K}_{p1}=3$ (ii) $A(g)\rightleftharpoons 2B(g){K}_{p2}=1$ If the degree of dissociation and initial concentration of both the reactants $X(g)$ and $A(g)$ are equal, then the ratio of the total pressure at equilibrium $(\frac{{p}_{1}}{{p}_{2}})$ is equal to $x:1$. The value of $x$ is (Nearest integer)

The vapour pressure of $30%(w/v)$, aqueous solution of glucose is ________ $\mathrm{mm}\mathrm{Hg}$ at ${25}^{\circ }C$. [Given: The density of $30%(w/v)$, aqueous solution of glucose is $1.2g{\mathrm{cm}}^{–3}$ and vapour pressure of pure water is $24\mathrm{mm}\mathrm{Hg}$.] (Molar mass of glucose is $180g{\mathrm{mol}}^{–1}$)

$20%$ of acetic acid is dissociated when its $5g$ is added to $500\mathrm{mL}$ of water. The depression in freezing point of such water is $_____\times {10}^{-3}C\circ$. Atomic mass of $C,H$ and $O$ are $12,1$ and $16$ a.m.u. respectively. [Given : Molal depression constant and density of water are $1.86K\mathrm{kg}{\mathrm{mol}}^{-1}$ and $1g{\mathrm{cm}}^{-3}$ respectively.

$28.0$ L of ${\mathrm{CO}}_{2}$ is produced on complete combustion of $16.8L$ gaseous mixture of ethene and methane at $25^{\circ}C$ and $1$ atm. Heat evolved during the combustion process is $\mathrm{kJ}$ Given$:{\Delta H}_{C}({\mathrm{CH}}_{4})=-900\mathrm{kJ}{\mathrm{mol}}^{-1}$ ${\Delta H}_{C}({C}_{2}{H}_{4})=-1400\mathrm{kJ}{\mathrm{mol}}^{-1}$.

Arrange the following orbitals in decreasing order of energy. A. $n=3,l=0,m=0$ B. $n=4,l=0,m=0$ C. $n=3,l=1,m=0$ D. $n=3,l=2,m=1$ The correct option for the order is:

When a hydrocarbon $A$ undergoes complete combustion it requires $11$ equivalents of oxygen and produces $4$ equivalents of water. What is the molecular formula of $A$?

The number of correct statements from the following is ___________ (A) Conductivity always decreases with decrease in concentration for both strong and weak electrolytes. (B) The number of ions per unit volume that carry current in a solution increases on dilution. (C) Molar conductivity increases with decrease in concentration. (D) The variation in molar conductivity is different for strong and weak electrolytes. (E) For weak electrolytes, the change in molar conductivity with dilution is due to decrease in degree of dissociation.