Physical Chemistry PYQ — Page 31

If the $\mathrm{pKa}$ of lactic acid is $5$, then the $\mathrm{pH}$ of $0.005M$ calcium lactate solution at $25^{\circ}C$ is __________ $\times {10}^{–1}$ (Nearest integer)

Solid fuel used in rocket is a mixture of ${\mathrm{Fe}}_{2}{O}_{3}$and $\mathrm{Al}$ (in ratio $1:2$). The heat evolved $(\mathrm{kJ})$ per gram of the mixture is _____ (Nearest integer) Given ${\Delta H}_{f}^{0}({\mathrm{Al}}_{2}{O}_{3})=-1700\mathrm{kJ}{\mathrm{mol}}^{-1}$ ${\Delta H}_{f}^{0}({\mathrm{Fe}}_{2}{O}_{3})=-840\mathrm{kJ}{\mathrm{mol}}^{-1}$ Molar mass of $\mathrm{Fe},\mathrm{AI}$ and $O$ are $56,27$ and $16g{\mathrm{mol}}^{–1}$ respectively

The number of atomic orbitals from the following having $5$ radial nodes is $7s,7p,6s,8p,8d$

Choose the correct representation of conductometric titration of benzoic acid vs sodium hydroxide.

If compound $A$ reacts with $B$ following first order kinetics with rate constant $2.011\times {10}^{-3}{s}^{-1}$. The time taken by A (in seconds) to reduce from $7g$ to $2g$ will be _____ . (Nearest Integer) $[\mathrm{log}5=0.698,\mathrm{log}7=0.845,\mathrm{log}2=0.301]$

The equilibrium composition for the reaction ${\mathrm{PCl}}_{3}+{\mathrm{Cl}}_{2}\underset{}{\rightleftharpoons }{\mathrm{PCl}}_{5}$ at $298K$ is given below: ${[{\mathrm{PCl}}_{3}]}_{\mathrm{eq}}=0.2\mathrm{mol}{L}^{-1},{[{\mathrm{Cl}}_{2}]}_{\mathrm{eq}}=0.1\mathrm{mol}{L}^{-1},{[{\mathrm{PCl}}_{5}]}_{\mathrm{eq}}=0.40\mathrm{mol}{L}^{-1}$ If $0.2\mathrm{mol}$ of ${\mathrm{Cl}}_{2}$ is added at the same temperature, the equilibrium concentrations of ${\mathrm{PCl}}_{5}$ is _____ $\times {10}^{–2}\mathrm{mol}{L}^{–1}$ Given: ${K}_{c}$ for the reaction at $298K$ is $20$

Values of work function $({W}_{0})$ for a few metals are given below <table class="pyq-table"><tbody><tr><td>Metal</td><td>$\mathrm{Li}$</td><td>$\mathrm{Na}$</td><td>$K$</td><td>$\mathrm{Mg}$</td><td>$\mathrm{Cu}$</td><td>$\mathrm{Ag}$</td></tr><tr><td>$\frac{{W}_{0}}{\mathrm{eV}}$</td><td>$2.42$</td><td>$2.3$</td><td>$2.25$</td><td>$3.7$</td><td>$4.8$</td><td>$4.3$</td></tr></tbody></table>The number of metals which will show photoelectric effect when light of wavelength $400\mathrm{nm}$ falls on it is _____ Given: $h=6.6\times {10}^{–34}Js$ $c=3\times {10}^{8}{\mathrm{ms}}^{–1}$ $e=1.6\times {10}^{–19}C$

The energy of an electron in the first Bohr orbit of hydrogen atom is $-2.18\times {10}^{-18}J$ Its energy in the third Bohr orbit is$_______.$

Which of the following statement(s) is/are correct? (A) The $\mathrm{pH}$ of $1\times {10}^{–8}M\mathrm{HCl}$ solution is $8$. (B) The conjugate base of ${H}_{2}{\mathrm{PO}}^{4-}$ is ${\mathrm{HPO}}_{4}^{2-}$. (C) ${K}_{w}$ increases with increase in temperature. (D) When a solution of a weak monoprotic acid is titrated against a strong base at half neutralisation point, $\mathrm{pH}=\frac{1}{2}{\mathrm{pK}}_{a}$. Choose the correct answer from the options given below:

$600\mathrm{mL}$ of $0.01M\mathrm{HCl}$ is mixed with $400\mathrm{mL}$ of $0.01M{H}_{2}{\mathrm{SO}}_{4}$. The $\mathrm{pH}$ of the mixture is _____$\times {10}^{-2}$. (Nearest integer) [Given $\mathrm{log}2=0.30,\mathrm{log}3=0.48,\mathrm{log}5=0.69,\mathrm{log}7=0.84,\mathrm{log}11=1.04$]

Assume that the radius of the first Bohr orbit of hydrogen atom is $0.6Å$. The radius of the third Bohr orbit of ${\mathrm{He}}^{+}$ is _____ picometer. (Nearest Integer)

In the depression of freezing point experiment A. Vapour pressure of the solution is less than that of pure solvent B. Vapour pressure of the solution is more than that of pure solvent C. Only solute molecules solidify at the freezing point D. Only solvent molecules solidify at the freezing point

See the following chemical reaction: ${\mathrm{Cr}}_{2}{O}_{7}^{2-}+{\mathrm{XH}}^{+}+6{\mathrm{Fe}}^{2+}\rightarrow {\mathrm{YCr}}^{3+}+6{\mathrm{Fe}}^{3+}+{\mathrm{ZH}}_{2}O$ The sum of X, Y and Z is

The standard electrode potential (${M}^{3+}/{M}^{2+}$) for $V,\mathrm{Cr},\mathrm{Mn}$ & $\mathrm{Co}$ are $-0.26V,-0.41V,+1.57V$ and $+1.97V$, respectively. The metal ions which can liberate ${H}_{2}$ from a dilute acid are

For a reversible reaction $A\rightleftharpoons B$, the $\Delta H$ forward reaction $=20\mathrm{kJ}{\mathrm{mol}}^{–1}$. The activation energy of the uncatalyzed forward reaction is $300\mathrm{kJ}{\mathrm{mol}}^{–1}$. When the reaction is catalysed keeping the reactant concentration same, the rate of the catalysed forward reaction at ${27}^{\circ }C$ is found to be same as that of the uncatalyzed reaction at ${327}^{\circ }C$. The activation energy of the catalysed backward reaction is _______$\mathrm{kJ}{\mathrm{mol}}^{–1}$.

One mole of an ideal monoatomic gas is subjected to changes as shown in the graph. The magnitude of the work done (by the system or on the system) is _______ J (nearest integer)  Given : log 2 = 0.3, ln 10 = 2.3

${\mathrm{FeO}}_{4}^{2-}\overset{+2.2V}{\longrightarrow }{\mathrm{Fe}}^{3+}\overset{+0.70V}{\longrightarrow }{\mathrm{Fe}}^{2+}\overset{-0.45V}{\longrightarrow }{\mathrm{Fe}}^{0}$ ${E}_{{\mathrm{FeO}}_{4}^{2-}/{\mathrm{Fe}}^{2+}}^{\theta }$ is $x\times {10}^{-3}V$. The value of $x$ is _______

If the radius of the first orbit of hydrogen atom is ${a}_{0}$, then de Broglie’s wavelength of electron in ${3}^{\mathrm{rd}}$ orbit is

An analyst wants to convert $1L\mathrm{HCl}$ of $\mathrm{pH}=1$ to a solution of $\mathrm{HCl}$ of $\mathrm{pH}=2$. The volume of water needed to do this dilution is _____ $\mathrm{mL}$. (Nearest integer)

At $298K$ ${N}_{2}(g)+3{H}_{2}(g)\rightleftharpoons 2{\mathrm{NH}}_{3}(g),{K}_{1}=4\times {10}^{5}$ ${N}_{2}(g)+{O}_{2}(g)\rightleftharpoons 2\mathrm{NO}(g),{K}_{2}=1.6\times {10}^{12}$ ${H}_{2}(g)+\frac{1}{2}{O}_{2}(g)\rightleftharpoons {H}_{2}O(g),{K}_{3}=1.0\times {10}^{-13}$ Based on above equilibria, the equilibrium constant of the reaction, $2{\mathrm{NH}}_{3}(g)+\frac{5}{2}{O}_{2}(g)\rightleftharpoons 2\mathrm{NO}(g)+3{H}_{2}O(g)$ is _____ $\times {10}^{-33}$ (Nearest integer)

One mole of an ideal gas at $350K$ is in a $2.0L$ vessel of thermally conducting walls, which are in contact with the surroundings. It undergoes isothermal reversible expansion from $2.0L$ to $3.0L$ against a constant pressure of $4\mathrm{atm}$. The change in entropy of the surroundings $(\Delta S)$ is _____ $J{K}^{–1}$ (Nearest integer) Given: $R=8.314J{K}^{-1}{\mathrm{mol}}^{-1}$.

The volume of $0.02M$ aqueous $\mathrm{HBr}$ required to neutralize $10.0\mathrm{mL}$ of $0.01M$ aqueous $\mathrm{Ba}(\mathrm{OH}{)}_{2}$ is (Assume complete neutralization)

Which of the following relations are correct? (A) $\Delta U=q+p\Delta V$ (B) $\Delta G=\Delta H-T\Delta S$ (C) $\Delta S=\frac{{q}_{\mathrm{rev}}}{T}$ (D) $\Delta H=\Delta U-\Delta nRT$ Choose the most appropriate answer from the options given below :

$0.3g$ of ethane undergoes combustion at $27^{\circ}C$ in a bomb calorimeter. The temperature of calorimeter system (including the water) is found to rise by $0.5^{\circ}C$. The heat evolved during combustion of ethane at constant pressure is ${\mathrm{kJmol}}^{-1}$. (Nearest integer) [Given : The heat capacity of the calorimeter system is $20\mathrm{kJ}{K}^{-1},R=8.3{\mathrm{JK}}^{-1}{\mathrm{mol}}^{-1}$. Assume ideal gas behaviour. Assume ideal gas behaviour. Atomic mass of $C$ and $H$ are $12$ and $1g{\mathrm{mol}}^{-1}$ respectively]