Physical Chemistry PYQ — Page 60

When an electric current is passes through acidified water, $112 \mathrm{~mL}$ of hydrogen gas at N.T.P. was collected at the cathode in $965$ seconds. The current passed, in ampere, is :

Following four solutions are prepared by mixing different volumes of $\mathrm{NaOH}$ and $\mathrm{HCl}$ of different concentrations, $\mathrm{pH}$ of which one of them will be equal to 1 ?

The gas phase reaction $2{\mathrm{NO}}_{2}(g) \rightarrow {N}_{2}{O}_{4} (g)$ is an exothermic reaction. The decomposition of ${N}_{2}{O}_{4}$ , in equilibrium mixture of ${\mathrm{NO}}_{2} (g) \mathrm{and} {N}_{2}{O}_{4} (g)$ can be increased by:

At a certain temperature in a 5L vessel, 2 moles of carbon monoxide and 3 moles of chlorine were allowed to reach equilibrium according to the reaction, $\mathrm{CO}+\mathrm{Cl}_2 \rightleftharpoons \mathrm{COCl}_2$. At equilibrium, if one mole of $\mathrm{CO}$ is present then equilibrium constant $\left(K_{\mathrm{c}}\right)$ for the reaction is:

How long (approximate) should water be electrolysed by passing through $100$$\mathrm{amperes}$current so that the oxygen released can completely burn $27.66g$ of diborane? (Atomic weight of $B=10.8u$)

Which of the following statements is false?

For a first order reaction, $\mathrm{A} \rightarrow \mathrm{P}, \mathrm{t}_{1 / 2}$ (half-life) is 10 days. The time required for $\frac{1}{4}^{\text {th }}$ conversion of $\mathrm{A}$ (in days) is: $(\ln 2=0.693, \ln 3=1.1)$.

${ \text{pK}}_{\text{a}}$ of a weak acid $( \text{HA})$ and ${ \text{pK}}_{\text{b}}$ of a weak base $( \text{BOH})$ are $3.2$ and $3.4$ respectively. The $\text{pH}$ of their salt $( \text{AB})$ solution at ${ \text{25}}^{\text{o}} \text{C}$ is

The rate of a reaction quadruples when the temperature changes from $300$ to $310K$ . The activation energy of this reaction is: (Assume Activation energy and pre-exponential factor are independent of temperature; $\mathrm{ln}(2)=0.693;R=8.314J{\mathrm{mol}}^{-1}{K}^{-1}$)

Among the following species which option contains all isoelectronic species?

Consider the following standard electrode potentials (${\text{E}}^{\text{o}}$ in volts) in aqueous solution: $\begin{matrix}\underset{}{\text{E}\text{l}\text{e}\text{m}\text{e}\text{n}\text{t}} & \underset{}{{\text{M}}^{3+}/\text{M}} & \underset{}{{\text{M}}^{+}/\text{M}} \\ \text{A}\text{l} & -1.66 & +0.55 \\ \text{T}\text{l} & +1.26 & -0.34\end{matrix}$ Based on these data, which of the following statements is correct?

Which of the following ions does not liberate hydrogen gas on reaction with dilute acids?

The pair of compounds having metals in their highest oxidation state is

$\text{Δ}\text{U}$ is equal to:

$5g$ of ${\mathrm{Na}}_{2}{\mathrm{SO}}_{4}$ was dissolved in $x g$ of ${H}_{2}O$ . The change in freezing point was found to be $3{.82}^{o}C$ . If ${\mathrm{Na}}_{2}{\mathrm{SO}}_{4}$ is $81.5%$ ionised, the value of $x$ ( ${K}_{f}$ for water $=1{.86}^{o}C \mathrm{kg} {\mathrm{mol}}^{-1}$ ) is approximately: (molar mass of $S=32 g {\mathrm{mol}}^{-1}$ and that of $\mathrm{Na}=23 g {\mathrm{mol}}^{-1}$ )

The electron in the hydrogen atom undergoes transition from higher orbitals to orbital of radius $211.6\mathrm{pm}$. This transition is associated with

The enthalpy change on freezing of $1\mathrm{mol}$ of water at $5^{\circ}C$ to ice at $-5^{\circ}C$ is: (Given ${\Delta }_{\mathrm{fus}} H=6 \mathrm{kJ} {\mathrm{mol}}^{-1}$ at $0^{\circ}C,$ ${C}_{p}({H}_{2}O, l)=75.3 J {\mathrm{mol}}^{-1}{K}^{-1}$ ${C}_{p}({H}_{2}O, s)=36.8 J {\mathrm{mol}}^{-1}{K}^{-1}$ )

An ideal gas undergoes isothermal expansion at constant pressure. During the process:

A gas undergoes change from state $A$ to state $B$. In this process, the heat absorbed and work done by the gas is $5J\text{and}8J$, respectively. Now gas is brought back to $A$ by another process during which $3J$ of heat is evolved. In this reverse process of $B\mathrm{to}A$.

$50 \mathrm{mL}$ of $0.2M$ ammonia solution is treated with $25\mathrm{mL}\mathrm{of}0.2M\mathrm{HCl}$. If ${\mathrm{pK}}_{b}$ of ammonia solution is $4.75$, the $\mathrm{pH}$ of the mixture will be:

If the shortest wavelength in Lyman series of hydrogen atom is $A$, then the longest wavelength in Paschen series of ${\mathrm{He}}^{+}$ is

The freezing point of benzene decreases by ${0.45}^{^{\circ}}C$ on adding $0.2 g$ of acetic acid to $20g$ of benzene. If acetic acid associates to form a dimer in benzene, then what is the percentage association of acetic acid in benzene? $({K}_{f}\mathrm{for} \mathrm{benzene}=5.12 K \mathrm{kg} {\mathrm{mol}}^{-1} )$

Excess of $\mathrm{NaOH}(\mathrm{aq})$ was added to $100\mathrm{mL}$ of ${\mathrm{FeCl}}_{3} (\mathrm{aq})$ resulting into $2.14g$ of $\mathrm{Fe}{(\mathrm{OH})}_{3}$. The molarity of ${\mathrm{FeCl}}_{3}(\mathrm{aq})$ is: (Given the molar mass of$\mathrm{Fe}=56g$${\mathrm{mol}}^{-1}$ and molar mass of $\mathrm{Cl}=35.5 g {\mathrm{mol}}^{-1}$)

To find the standard potential of ${M}^{3+}/M$ electrode, the following cell is constituted: $\mathrm{Pt}/M/{M}^{3+} (0.001 \mathrm{mol} {L}^{-1})/{\mathrm{Ag}}^{+} (0.01 \mathrm{mol} {L}^{-1})/\mathrm{Ag}$ The emf of the cell is found to be $0.421\mathrm{volt}$ at $298K$. The standard potential of half-reaction ${M}^{3+}+3{e}^{-}\rightarrow M$ at $298K$ will be: (Given: ${E}_{\frac{{\mathrm{Ag}}^{+}}{\mathrm{Ag}}}^{\circleddash }$ at $298K=0.80\mathrm{volt}$)