Physical Chemistry PYQ — Page 44

The standard enthalpies of formation of ${\mathrm{Al}}_{2}{O}_{3}$ and $\mathrm{CaO}$ are $-1675\mathrm{kJ}{\mathrm{mol}}^{-1}$ and $-635\mathrm{kJ}{\mathrm{mol}}^{-1}$ respectively. For the reaction $3\mathrm{CaO}+2\mathrm{Al}\rightarrow 3\mathrm{Ca}+{\mathrm{Al}}_{2}{O}_{3}$ the standard reaction enthalpy ${\Delta }_{r}{H}^{0}=$ ________ $\mathrm{kJ}.$ (Round off to the Nearest Integer).

At $25^{\circ}C,50g$ of iron reacts with $\mathrm{HCl}$ to form ${\mathrm{FeCl}}_{2}$. The evolved hydrogen gas expands against a constant pressure of $1\mathrm{bar}$. The work done by the gas during this expansion is -_______ $J$. (Round off to the Nearest Integer) [Given : $R=8.314J{\mathrm{mol}}^{-1}{K}^{-1}$. Assume, hydrogen is an ideal gas] [Atomic mass off Fe is $55.85u$]

Five moles of an ideal gas at $293K$ is expanded isothermally from an initial pressure of $2.1\mathrm{MPa}$ to $1.3\mathrm{MPa}$ against at constant external pressure $4.3\mathrm{MPa}$. The heat transferred in this process is ___ ${\mathrm{kJmol}}^{-1}$. (Rounded-off to the nearest integer)[ Use $R=8.314J{\mathrm{mol}}^{-1}{K}^{-1}$]

The reaction of sulphur in alkaline medium is given below: ${S}_{8(s)}+a{\mathrm{OH}}_{(\mathrm{aq})}^{-}\rightarrow b{S}_{(\mathrm{aq})}^{2-}+c{S}_{2}{O}_{3(\mathrm{aq})}^{2-}+d{H}_{2}{O}_{(l)}$ The values of '$a$' is______ (Integer answer)

The ${\mathrm{OH}}^{-}$ concentration in a mixture of $5.0\mathrm{mL}$ of $0.0504M{\mathrm{NH}}_{4}\mathrm{Cl}$ and $2\mathrm{mL}$ of $0.0210M{\mathrm{NH}}_{3}$ solution is $x\times {10}^{-6}M$. The value of $x$ is (Nearest integer) [Given ${K}_{w}=1\times {10}^{-14}$ and ${K}_{b}=1.8\times {10}^{-5}]$

The number of moles of ${\mathrm{NH}}_{3},$ that must be added to $2L$ of $0.80{\mathrm{MAgNO}}_{3}$ in order to reduce the concentration of ${\mathrm{Ag}}^{+}$ ions to $5.0\times {10}^{-8}M({K}_{\text{formation }}$ for ${[\mathrm{Ag}{({\mathrm{NH}}_{3})}_{2}]}^{+}=1.0\times {10}^{8})$ is __________. (Nearest integer) [Assume no volume change on adding ${\mathrm{NH}}_{3}$]

$2{\mathrm{SO}}_{2}(g)+{O}_{2}(g)\rightleftharpoons 2{\mathrm{SO}}_{3}(g)$ In an equilibrium mixture, the partial pressures are ${P}_{{\mathrm{SO}}_{3}}=43\mathrm{kPa};{P}_{{O}_{2}}=530\mathrm{Pa}$ and ${P}_{{\mathrm{SO}}_{2}}=45\mathrm{kPa}.$ The equilibrium constant ${K}_{P}=_____\times {10}^{-2}.$ (Nearest integer)

Which one of the following species doesn't have a magnetic moment of $1.73\mathrm{BM},$ (spin only value)?

A system does $200J$ of work and at the same time absorbs $150J$ of heat. The magnitude of the change in internal energy is ______$J$. (Nearest integer)

The decomposition of formic acid on gold surface follows first order kinetics. If the rate constant at $300K$ is $1.0\times {10}^{-3}{s}^{-1}$ and the activation energy ${E}_{a}=11.488\mathrm{kJ}{\mathrm{mol}}^{-1}$, the rate constant at $200K$ is _________ $\times {10}^{-5}{s}^{-1}$. (Round of to the Nearest Integer). (Given $R=8.314J{\mathrm{mol}}^{-1}{K}^{-1}$)

In the sulphur estimation, $0.471g$ of an organic compound gave $1.44g$ of barium sulfate. The percentage of sulphur in the compound is. (Nearest integer) (Atomic Mass of $\mathrm{Ba}=137u$ )

An exothermic reaction $X\rightarrow Y$ has an activation energy $30\mathrm{kJ}{\mathrm{mol}}^{-1}$. If energy change $\Delta E$ during the reaction is $-20\mathrm{kJ}$, then the activation energy for the reverse reaction in $\mathrm{kJ}$ is (Integer answer)

The incorrect expression among the following is :

For the reaction $2{\mathrm{NO}}_{2}(g)\rightleftharpoons {N}_{2}{O}_{4}(g),$ when $\Delta S=-176.0J{K}^{-1}$ and $\Delta H=-57.8\mathrm{kJ}{\mathrm{mol}}^{-1}$ the magnitude of $\Delta G$ at $298K$ for the reaction is _____ ${\mathrm{kJmol}}^{-1}$. (Nearest integer)

The molar conductivity at infinite dilution of barium chloride, sulphuric arid and hydrochloric acid are $280,860$ $426{\mathrm{Scm}}^{2}{\mathrm{mol}}^{-1}$ respectively. The molar conductivity at infinite dilution of barium sulphate is ___ ${\mathrm{Scm}}^{2}{\mathrm{mol}}^{-1}$ ( Round off to the Nearest Integer).

$2$ molal solution of a weak acid $\mathrm{HA}$ has a freezing point of $3.885^{\circ}C.$ The degree of dissociation of this acid is ______$\times {10}^{-3}.$ (Round off to the Nearest Integer). $[$Given : Molal depression constant of water $=1.85K\mathrm{kg}{\mathrm{mol}}^{-1}$ Freezing point of pure water$=0^{\circ}C]$

The resistance of conductivity cell with cell constant $1.14{\mathrm{cm}}^{-1}$, containing $0.001M\mathrm{KCl}$ at $298K$ is $1500\Omega$. The molar conductivity of $0.001M\mathrm{KCl}$ solution at $298K$ in $S{\mathrm{cm}}^{2}{\mathrm{mol}}^{-1}$ is (Integer answer)

$1\mathrm{kg}$ of $0.75$ molal aqueous solution of sucrose can be cooled up to $-4^{\circ}C$ before freezing. The amount of ice (in $g$) that will be separated out is ___________. (Nearest integer) [Given : ${K}_{f}({H}_{2}O)=1.86K\mathrm{kg}{\mathrm{mol}}^{-1}$]

$10.0\mathrm{ml}$ of ${\mathrm{Na}}_{2}{\mathrm{CO}}_{3}$ solution is titrated against $0.2M\mathrm{HCl}$ solution. The following values were obtained in $5$ readings. $4.8\mathrm{ml},4.9\mathrm{ml},5.0\mathrm{ml},5.0\mathrm{ml}$ and $5.0\mathrm{ml}$ Based on these readings, and convention of titrimetric estimation of concentration of ${\mathrm{Na}}_{2}{\mathrm{CO}}_{3}$ solution is ___ $\mathrm{mM}$. (Round off to the Nearest integer)

Assuming ideal behaviour, the magnitude of $\mathrm{log}K$ for the following reaction at $25^{\circ}C$ is $x\times {10}^{-1}.$ The value of $x$ is __________. (Integer answer)$3\mathrm{HC}\equiv {\mathrm{CH}}_{(g)}\rightleftharpoons {C}_{6}{H}_{6(l)}$ [Given: ${\Delta }_{f}G^{\circ}(\mathrm{HC}\equiv \mathrm{CH})=-2.04\times {10}^{5}J{\mathrm{mol}}^{-1};{\Delta }_{f}G^{\circ}({C}_{6}{H}_{6})=-1.24\times {10}^{5}J{\mathrm{mol}}^{-1};R=8.314J{K}^{-1}{\mathrm{mol}}^{-1}$]

$15\mathrm{mL}$ of aqueous solution of ${\mathrm{Fe}}^{2+}$ in acidic medium completely reacted with $20\mathrm{mL}$ of $0.03M$ aqueous ${\mathrm{Cr}}_{2}{{O}_{7}}^{2-}.$ The molarity of the ${\mathrm{Fe}}^{2+}$ solution is _______ $\times {10}^{-2}M$ (Round off to the Nearest Integer).

When $10\mathrm{mL}$ of an aqueous solution of ${\mathrm{Fe}}^{2+}$ ions was titrated in the presence of dil ${H}_{2}{\mathrm{SO}}_{4}$ using diphenylamine indicator, $15\mathrm{mL}$ of $0.02M$ solution of ${K}_{2}{\mathrm{Cr}}_{2}{O}_{7}$ was required to get the end point. The molarity of the solution containing ${\mathrm{Fe}}^{2+}$ ions is $x\times {10}^{-2}M$. The value of $x$ is ______. (Nearest integer)

Given below are two statements: Statement I : Bohr's theory accounts for the stability and line spectrum of ${\mathrm{Li}}^{+}$ ion. Statement II : Bohr's theory was unable to explain the splitting of spectral lines in the presence of a magnetic field. In the light of the above statements, choose the most appropriate answer from the options given below:

Complete combustion of $1.80g$ of an oxygen containing compound $({C}_{x}{H}_{y}{O}_{z})$ gave $2.64g$ of ${\mathrm{CO}}_{2}$ and $1.08g$ of ${H}_{2}O.$ The percentage of oxygen in the organic compound is :