Physical Chemistry PYQ — Page 45

The reaction $2A+{B}_{2}\rightarrow 2\mathrm{AB}$ is an elementary reaction. For a certain quantity of reactants, if the volume of the reaction vessel is reduced by a factor of $3,$ the rate of the reaction increases by a factor of _____ . (Round off to the Nearest Integer).

Sulphurous acid $({H}_{2}{\mathrm{SO}}_{3})$ has ${\mathrm{Ka}}_{1}=1.7\times {10}^{-2}$ and ${\mathrm{Ka}}_{2}=6.4\times {10}^{-8}.$ The $\mathrm{pH}$ of $0.588M{H}_{2}{\mathrm{SO}}_{3}$ is____________ $($Round off to the Nearest Integer$)$.

A source of monochromatic radiation wavelength $400\mathrm{nm}$ provides $1000J$ of energy in $10$ seconds. When this radiation falls on the surface of sodium, $x\times {10}^{20}$ electrons are ejected per second. Assume that wavelength $400\mathrm{nm}$ is sufficient for ejection of electron from the surface of sodium metal. The value of $x$ is ______. (Nearest integer) $(h=6.626\times {10}^{-34}\mathrm{Js})$

An aqueous $\mathrm{KCl}$ solution of density $1.20g{\mathrm{mL}}^{-1}$ has a molality of $3.30\mathrm{mol}{\mathrm{kg}}^{-1}$. The molarity of the solution in ${\mathrm{molL}}^{-1}$ is____.(The Nearest integer) $[$Molar mass of $\mathrm{KCl}=74.5g]$

Data given for the following reaction is as follows : ${\mathrm{FeO}}_{(s)}+{C}_{(\mathrm{graphite})}\longrightarrow {\mathrm{Fe}}_{(s)}+{\mathrm{CO}}_{(g)}$ <table class="pyq-table"><tbody><tr><td>Substance</td><td>${\Delta }_{f}H^{\circ}({\mathrm{kJmol}}^{-1})$</td><td>$\Delta S^{\circ}({\mathrm{Jmol}}^{-1}{K}^{-1})$</td></tr><tr><td>${\mathrm{FeO}}_{(s)}$</td><td>$-266.3$</td><td>$57.49$</td></tr><tr><td>${C}_{(\mathrm{graphite})}$</td><td>$0$</td><td>$5.74$</td></tr><tr><td>${\mathrm{Fe}}_{(s)}$</td><td>$0$</td><td>$27.28$</td></tr><tr><td>${\mathrm{CO}}_{(g)}$</td><td>$-110.5$</td><td>$197.6$</td></tr></tbody></table>The minimum temperature in $K$ at which the reaction becomes spontaneous is_____.(Integer answer)

If the activation energy of a reaction is $80.9\mathrm{kJ}{\mathrm{mol}}^{-1}$, the fraction of molecules at $700K$, having enough energy to react to form products is ${e}^{-x}$. The value of $x$ is (Rounded off to the nearest integer) [Use $R=8.31J{K}^{-1}{\mathrm{mol}}^{-1}$]

For the reaction $A(g)\rightleftharpoons B(g)$ at $495K$, ${\Delta }_{r}{G}^{^{\circ}}=-9.478\mathrm{kJ}{\mathrm{mol}}^{-1}$ If we start the reaction in a closed container at $495K$ with $22$ millimoles of $A$, the amount of $B$ is the equilibrium mixture is ________ millimoles. (Round off to the Nearest Integer). $[R=8.314J{\mathrm{mol}}^{-1}{K}^{-1};\ell n10=2.303]$

The formula of a gaseous hydrocarbon which requires 6 times of its own volume of ${O}_{2}$ for complete oxidation and produces $4$ times its own volume of ${\mathrm{CO}}_{2}$ is ${C}_{x}{H}_{y}.$ The value of $y$ is ________.

The reaction of cyanamide, ${\mathrm{NH}}_{2}{\mathrm{CN}}_{(s)}$ with oxygen was run in a bomb calorimeter and $\Delta U$ was found to be $-742.24\mathrm{kJ}{\mathrm{mol}}^{-1}$ . The magnitude of ${\Delta H}_{298}$ for the reaction ${\mathrm{NH}}_{2}{\mathrm{CN}}_{(s)}+\frac{3}{2}{O}_{2(g)}\rightarrow {N}_{2(g)}+{O}_{2(g)}+{H}_{2}{O}_{(l)}$ is $\mathrm{kJ}$. (Rounded off to the nearest integer) [Assume ideal gases and $R=8.314J{\mathrm{mol}}^{-1}{K}^{-1}$]

When $9.45g$ of ${\mathrm{ClCH}}_{2}\mathrm{COOH}$ is added to $500\mathrm{mL}$ of water, its freezing point drops by $0.5^{\circ}C.$ The dissociation constant of ${\mathrm{ClCH}}_{2}\mathrm{COOH}$ is $x\times {10}^{-3}.$ The value of $x$ is off to the nearest integer) $[{K}_{f({H}_{2}O)}=1.86K\mathrm{kg}{\mathrm{mol}}^{-1}]$

At $1990K$ and $1\mathrm{atm}$ pressure, there are equal number of ${\mathrm{Cl}}_{2}$ molecules and $\mathrm{Cl}$ atoms in the reaction mixture. The value of ${K}_{p}$ for the reaction ${\mathrm{Cl}}_{2(g)}=2{\mathrm{Cl}}_{(g)}$ under the above conditions is $x\times {10}^{-1}.$ The value of $x$ is______(Rounded off to the nearest integer)

When $400\mathrm{mL}$ of $0.2M{H}_{2}{\mathrm{SO}}_{4}$ solution is mixed with $600\mathrm{mL}$ of $0.1\mathrm{MNaOH}$ solution, the increase in temperature of the final solution is $—\times {10}^{-2}K$. (Round off to the nearest integer). [Use :${H}^{+}(\mathrm{aq})+{\mathrm{OH}}^{-}(\mathrm{aq})\rightarrow {H}_{2}O:$${\Delta }_{\gamma }H=-57.1\mathrm{kJ}{\mathrm{mol}}^{-1}]$ Specific heat of ${H}_{2}O=4.18J{K}^{-1}{g}^{-1}$ , density of ${H}_{2}O=1.0g{\mathrm{cm}}^{-3}$ Assume no change in volume of solution on mixing.

For a given chemical reaction $A\rightarrow B$ at $300K$ the free energy change is $-49.4\mathrm{kJ}{\mathrm{mol}}^{-1}$ and the enthalpy of reaction is $51.4\mathrm{kJ}{\mathrm{mol}}^{-1}.$ The entropy change of the reaction is _________${\mathrm{JK}}^{-1}{\mathrm{mol}}^{-1}.$

For the reaction, $\mathrm{aA}+\mathrm{bB}\rightarrow \mathrm{cC}+\mathrm{dD},$ the plot of $\mathrm{log}k$ v/s $\frac{1}{T}$ is given below:  The temperature at which the rate constant of the reaction is ${10}^{-4}{s}^{-1}$ is _____ $K.$ (Rounded-off to the nearest integer) [Given : The rat5e constant of the reaction is ${10}^{-5}{s}^{-1}$ at $500K$.]

${C}_{6}{H}_{6}$ freezes at $5.5^{\circ}C.$ The temperature at which a solution of $10g$ of ${C}_{4}{H}_{10}$ in $200g$ of ${C}_{6}{H}_{6}$ freeze is _______$C\circ .$ (nearest integer value), (The molal freezing point depression constant of ${C}_{6}{H}_{6}$ is $5.12^{\circ}C/m.$)

The solubility product of ${\mathrm{PbI}}_{2}$ is $8.0\times {10}^{-9}.$ The solubility of lead iodide in $0.1$ molar solution of lead nitrate is $x\times {10}^{-6}\mathrm{mol}/L.$ The value of $x$ is _________ (Rounded off to the nearest integer)[Given $\sqrt{2}=1.41$]

$100g$ of propane is completely reacted with $1000g$ of oxygen. The mole fraction of carbon dioxide in the resulting mixture is $x\times {10}^{-2}$. The value of $x$ is (Nearest integer)

In mildly alkaline medium, thiosulphate ion is oxidized by ${\mathrm{MnO}}_{4}^{-}$ to $"A"$. The oxidation state of sulphur in $"A"$ is_

The number of orbitals with $n=5,{m}_{1}=+2$ is ________. (Round off to the Nearest Integer).

$2{\mathrm{SO}}_{2}(g)+{O}_{2}(g)\rightarrow 2{\mathrm{SO}}_{3}(g)$ The above reaction is carried out in a vessel starting with partial pressure ${P}_{{\mathrm{SO}}_{2}}=250m\mathrm{bar}$, ${P}_{{O}_{2}}=750m\mathrm{bar}$ and ${P}_{{\mathrm{SO}}_{3}}=0\mathrm{bar}$. When the reaction is complete, the total pressure in the reaction vessel is _____ $m\mathrm{bar}$. (Round off of the nearest integer).

A $6.50$ molal solution of $\mathrm{KOH}(\mathrm{aq}.)$ has a density of $1.89g{\mathrm{cm}}^{-3}$. The molarity of the solution is $\mathrm{mol}{\mathrm{dm}}^{-3}$. (Round off to the Nearest Integer). [Atomic masses: $K:39.0u;O:16.0u;H:1.0u$]

According to the following figure, the magnitude of the enthalpy change of the reaction $A+B\rightarrow M+N$ in $\mathrm{kJ}{\mathrm{mol}}^{-1}$ is equal to __________ . (Integer answer) 

When $3.00g$ of a substance $X$' is dissolved in $100g$ of ${\mathrm{CCl}}_{4}$, it raises the boiling point by $0.60K$. The molar mass of the substance ' ${X}^{'}$ is ___ g ${\mathrm{mol}}^{-1}$. (Nearest integer). [Given ${K}_{b}$ for ${\mathrm{CCl}}_{4}$ is $5.0K\mathrm{kg}{\mathrm{mol}}^{-1}]$

The conductivity of a weak acid$\mathrm{HA}$ of concentration $0.001\mathrm{mol}{L}^{-1}$ is $2.0\times {10}^{-5}S{\mathrm{cm}}^{-1}$. If ${\Lambda }_{m}^{0}(\mathrm{HA})=190S{\mathrm{cm}}^{2}{\mathrm{mol}}^{-1},$ the ionization constant $({K}_{a})$ of HA is equal to $____$ $\times {10}^{-6}$ (Round off to the Nearest Integer)