Physical Chemistry PYQ — Page 37

Assuming $1\mu g$ of trace radioactive element $X$ with a half life of $30$ years is absorbed by a growing tree. The amount of $X$ remaining in the tree after $100$ years is_____$\times {10}^{-1}\mu g$. [Given : $\mathrm{ln}10=2.303;\mathrm{log}2=0.30$]

A $0.166g$ sample of an organic compound was digested with conc. ${H}_{2}{\mathrm{SO}}_{4}$ and then distilled with $\mathrm{NaOH}$. The ammonia gas evolved was passed through $50.0\mathrm{mL}$ of $0.5N{H}_{2}{\mathrm{SO}}_{4}$. The used acid required $30.0\mathrm{mL}$ of $0.25N\mathrm{NaOH}$ for complete neutralization. The mass percentage of nitrogen in the organic compound is

The cell potential for the following cell $\mathrm{Pt}|{H}_{2}(g)|{H}^{+}(\mathrm{aq})||{\mathrm{Cu}}^{2+}(0.01M)|\mathrm{Cu}(s)$ is $0.576V$ at $298K$. The $\mathrm{pH}$ of the solution is (Nearest integer) (Given : ${E}_{{\mathrm{Cu}}^{2+}/\mathrm{Cu}}^{o}=0.34V$ and $\frac{2.303\mathrm{RT}}{F}=0.06V$)

The activation energy of one of the reactions in a biochemical process is $532611J{\mathrm{mol}}^{-1}$. When the temperature falls from $310K$ to $300K$, the change in rate constant observed is ${k}_{300}=x\times {10}^{-3}{k}_{310^{\circ}}$. The value of $x$ is [Given: $\mathrm{ln}10=2.3R=8.3J{K}^{-1}{\mathrm{mol}}^{-1}$]

When the excited electron of a $H$ atom from $n=5$ drops to the ground state, the maximum number of emission lines observed are

The moles of methane required to produce $81g$ of water after complete combustion is____$\times {10}^{-2}\mathrm{mol}$. [nearest integer]

The pair, in which ions are isoelectronic with ${\mathrm{Al}}^{3+}$ is

The rate constants for decomposition of acetaldehyde have been measured over the temperature range $700-1000K$. The data has been analysed by plotting $\mathrm{lnk}$ vs $\frac{{10}^{3}}{T}$ graph. The value of activation energy for the reaction is ${\mathrm{kJmol}}^{-1}$. (Nearest integer) (Given : $R=8.31J{K}^{-1}{\mathrm{mol}}^{-1}$) 

Assertion: The amphoteric behaviour of water is explained by Lewis acid base theory Reason: water acts as acid with ${\mathrm{NH}}_{3}$ and base with ${H}_{2}S$

The equation $k=(6.5\times {10}^{12}{s}^{-1}){e}^{-26000K/T}$ is followed for the decomposition of compound $A$. The activation energy for the reaction is ____ $\mathrm{KJ}{\mathrm{mol}}^{-1}$. [nearest integer] (Given: $R=8.314J{K}^{-1}{\mathrm{mol}}^{-1}$)

In the given reaction, $X+Y+3Z⇄{\mathrm{XYZ}}_{3}$ if one mole of each of $X$ and $Y$ with $0.05\mathrm{mol}$ of $Z$ gives compound ${\mathrm{XYZ}}_{3}$. (Given : Atomic masses of $X,Y$ and $Z$ are 10,20 and $30\mathrm{amu}$, respectively). The yield of ${\mathrm{XYZ}}_{3}$ is____$g$.

At $345K$, the half life for the decomposition of a sample of a gaseous compound initially at $55.5\mathrm{kPa}$ was $340s$. When the pressure was $27.8\mathrm{kPa}$, the half life was found to be $170s$. The order of the reaction is - [integer answer]

The standard free energy change $(\Delta G^{\circ})$ for $50%$ dissociation of ${N}_{2}{O}_{4}$ into ${\mathrm{NO}}_{2}$ at $27^{\circ}C$ and $1\mathrm{atm}$ pressure is $-xJ{\mathrm{mol}}^{-1}$. The value of $x$ is $-.....J$. (Nearest Integer) [Given : $R=8.31J{K}^{-1}{\mathrm{mol}}^{-1},\mathrm{log}1.33=0.1239\mathrm{ln}10=2.3$]

The standard electrode potential of hydrogen electrode at pH = 7 is:

Which of the following relation is not correct?

$2{O}_{3}(g)\rightleftharpoons 3{O}_{2}(g)$ At $300K$, ozone is fifty percent dissociated. The standard free energy change at this temperature and $1\mathrm{atm}$ pressure is $(-)......J{\mathrm{mol}}^{-1}$. (Nearest integer) [Given: $\mathrm{ln}1.35=0.3$ and $R=8.3J{K}^{-1}{\mathrm{mol}}^{-1}$]

${p}^{H}$ value of $0.001\mathrm{MNaOH}$ solution is

'$x$' $g$ of molecular oxygen $({O}_{2})$ is mixed with $200g$ of neon $(\mathrm{Ne})$. The total pressure of the nonreactive mixture of ${O}_{2}$ and $\mathrm{Ne}$ in the cylinder is $25$ bar. The partial pressure of $\mathrm{Ne}$ is $20$ bar at the same temperature and volume. The value of '$x$' is [Given: Molar mass of ${O}_{2}=32g{\mathrm{mol}}^{-1}$. Molar mass of $\mathrm{Ne}=20g{\mathrm{mol}}^{-1}$]

For the given reactions ${\mathrm{Sn}}^{2+}+2{e}^{-}\rightarrow \mathrm{Sn}$ ${\mathrm{Sn}}^{4+}+4{e}^{-}\rightarrow \mathrm{Sn}$ the electrode potentials are ; ${E}_{{\mathrm{Sn}}^{2+}/\mathrm{Sn}}^{^{\circ}}=-0.140V$ and ${E}_{{\mathrm{Sn}}^{4+}/\mathrm{Sn}}^{^{\circ}}=0.010V$. The magnitude of standard electrode potential for ${\mathrm{Sn}}^{4+}/{\mathrm{Sn}}^{2+}$ i.e. ${E}_{{\mathrm{Sn}}^{4+}/{\mathrm{Sn}}^{2+}}^{^{\circ}}$ is____$\times {10}^{-2}V$(Nearest integer)

At $310K$, the solubility of ${\mathrm{CaF}}_{2}$ in water is $2.34\times {10}^{-3}g/100\mathrm{mL}$. The solubility product of ${\mathrm{CaF}}_{2}$ is ---- $\times {10}^{-8}{(\mathrm{mol}/L)}^{3}$(nearest integer). (Given molar mass : ${\mathrm{CaF}}_{2}=78g{\mathrm{mol}}^{-1}$)

Which of the following sets of quantum numbers is not allowed?

${K}_{a}$ for butyric acid $({C}_{3}{H}_{7}\mathrm{COOH})$ is $2\times {10}^{-5}$. The$\mathrm{pH}$ of $0.2M$ solution of butyric acid is____$\times {10}^{-1}$. (Nearest integer) [Given $\mathrm{log}2=0.30$]

Resistance of a conductivity cell (cell constant $129{m}^{-1}$) filled with $74.5\mathrm{ppm}$ solution of $\mathrm{KCl}$ is $100\Omega$ (labelled as solution $1$). When the same cell is filled with $\mathrm{KCl}$ solution of $149\mathrm{ppm}$, the resistance is $50\Omega$ (labelled as solution $2$). The ratio of molar conductivity of solution $1$ and solution $2$ is i.e. $\frac{{\wedge }_{1}}{{\wedge }_{2}}=x\times {10}^{-3}$. The value of $x$ is____Given, molar mass of $\mathrm{KCl}$ is $74.5g{\mathrm{mol}}^{-1}$)

In a cell, the following reactions take place ${\mathrm{Fe}}^{2+}\rightarrow {\mathrm{Fe}}^{3+}+{e}^{-}{{E}^{o}}_{{\mathrm{Fe}}^{3+}/{\mathrm{Fe}}^{2+}}=0.77V$ $2{I}^{-}\rightarrow {I}_{2}+2{e}^{-}{E}_{{I}_{2}/{I}^{-}}^{0}=0.54V$ The standard electrode potential for the spontaneous reaction in the cell is $x\times {10}^{-2}V\mathrm{at}298K$. The value of $x$ is - (Nearest Integer)