Physical Chemistry PYQ — Page 38

$250g$ solution of $D$-glucose in water contains $10.8%$ of carbon by weight. The molality of the solution is nearest to (Given: Atomic Weights are $H=1u;C=12u;O=16u$)

Class $\mathrm{XII}$ students were asked to prepare one litre of buffer solution of $\mathrm{pH}8.26$ by their chemistry teacher. The amount of ammonium chloride to be dissolved by the student in $0.2M$ ammonia solution to make one litre of the buffer is (Given ${\mathrm{pK}}_{b}({\mathrm{NH}}_{3})=4.74;$ Molar mass of ${\mathrm{NH}}_{3}=17g{\mathrm{mol}}^{-1}$. Molar mass of ${\mathrm{NH}}_{4}\mathrm{Cl}=53.5g{\mathrm{mol}}^{-1}$)

A $1.84\mathrm{mg}$ sample of polyhydric alcoholic compound '$X$' of molar mass $92.0g/\mathrm{mol}$ gave $1.344\mathrm{mL}$ of ${H}_{2}$ gas at STP. The number of alcoholic hydrogen present in compound '$X$' is

The molar conductivity of a conductivity cell filled with $10$ moles of $20\mathrm{mL}\mathrm{NaCl}$ solution is ${\Lambda }_{m1}$ and that of $20$ moles another identical cell heaving $80\mathrm{mL}\mathrm{NaCl}$ solution is ${\Lambda }_{m2}$, The conductivities exhibited by these two cells are same. The relationship between ${\Lambda }_{m2}$ and ${\Lambda }_{m1}$ is

A gas ( Molar mass $=280g{\mathrm{mol}}^{-1}$) was burnt in excess ${O}_{2}$ in a constant volume calorimeter and during combustion the temperature of calorimeter increased from $298.0K$ to $298.45K$. If the heat capacity of calorimeter is $2.5\mathrm{kJ}{K}^{-1}$ and enthalpy of combustion of gas is $9\mathrm{kJ}{\mathrm{mol}}^{-1}$ then amount of gas burnt is____$g$.

A solution containing $2.5\times {10}^{-3}\mathrm{kg}$ of a solute dissolved in $75\times {10}^{-3}\mathrm{kg}$ of water boils at $373.535K$. The molar mass of the solute is ${\mathrm{mol}}^{-1}\cdot$ [nearest integer] (Given : ${K}_{b}({H}_{2}O)=0.52K\mathrm{kg}{\mathrm{mol}}^{-1}$ and boiling point of water $=373.15K$)

A flask is filled with equal moles of $A$ and $B$. The half lives of $A$ and $B$ are $100s$ and $50s$ respectively and are independent of the initial concentration. The time required for the concentration of $A$ to be four times that of $B$ is____$s$. (Given : $\mathrm{ln}2=0.693$)

A dilute solution of sulphuric acid is electrolysed using a current of $0.10A$ for $2$ hours to produce hydrogen and oxygen gas. The total volume of gases produced at $\mathrm{STP}$ is ${\mathrm{cm}}^{3}$. (Nearest integer) [Given : Faraday constant $F=96500{\mathrm{Cmol}}^{-1}$ at $\mathrm{STP}$, molar volume of an ideal gas is $22.7L{\mathrm{mol}}^{-1}$]

Manganese $(\mathrm{VI})$ has ability to disproportionate in acidic solution. The difference in oxidation states of two ions it forms in acidic solution is

Consider the following statements : (A) The principal quantum number '$n$' is a positive integer with values of '$n$' $=1,2,3,\ldots$ (B) The azimuthal quantum number '$l$' for a given '$n$' (principal quantum number) can have values as '$l$' $=0,1,2,\ldots .n$ has $(2n+1)$ values. (C) Magnetic orbital quantum number '$\mathrm{m}$' for a particular '$\mathrm{l}$' (azimuthal quantum number) has $(2\mathrm{l}+1)$ values. (D) $\pm \frac{1}{2}$ are the two possible orientations of electron spin. (E) For $l=5$, there will be a total of $9$ orbital Which of the above statements are correct?

The rate constant for a first order reaction is given by the following equation : $\mathrm{lnk}=33.24-\frac{2.0\times {10}^{4}K}{T}$ The Activation energy for the reaction is given by ${\mathrm{kJmol}}^{-1}$. (In Nearest integer) (Given : $R=8.3J{K}^{-1}{\mathrm{mol}}^{-1}$)

Consider the following pairs of electrons (A) (a) $n=3,l=1,{m}_{l}=1,{m}_{s}=+\frac{1}{2}$ (b) $n=3,l=2,{m}_{l}=1,{m}_{s}=+\frac{1}{2}$ (B) (a) $n=3,l=2,{m}_{l}=-2,{m}_{s}=-\frac{1}{2}$ (b) $n=3,l=2,{m}_{l}=-1,{m}_{s}=-\frac{1}{2}$ (C) (a) $n=4,l=2,{m}_{l}=2,{m}_{s}=+\frac{1}{2}$ (b) $n=3,l=2,{m}_{l}=2,{m}_{s}=+\frac{1}{2}$ The pairs of electrons present in degenerate orbitals is/are

 In the above reaction, $5g$ of toluene is converted into benzaldehyde with $92%$ yield. The amount of benzaldehyde produced is____ $\times {10}^{-2}g$

For the given first order reaction $A\rightarrow B$ the half life of the reaction is $0.3010\mathrm{min}$. The ratio of the initial concentration of reactant to the concentration of reactant at time $2.0\mathrm{min}$ will be equal to _____. (Nearest integer)

The cell potential for the given cell at $298K\mathrm{Pt}|{H}_{2}(g,1\mathrm{bar})||{H}^{+}(\mathrm{aq})\|{\mathrm{Cu}}^{2+}(\mathrm{aq})|\mathrm{Cu}(s)$ is $0.31V$. The $\mathrm{pH}$ of the acidic solution is found to be $3$, whereas the concentration of ${\mathrm{Cu}}^{2+}$ is ${10}^{x}M$. The value of $x$ is _________. (Given: ${E}_{{\mathrm{Cu}}^{2+}/\mathrm{Cu}}^{\Theta }=0.34V$ and $\frac{2.303\mathrm{RT}}{F}=0.06V$)

For a cell, $\mathrm{Cu}(s){\mathrm{Cu}}^{2+}(0.001M)|{\mathrm{Ag}}^{+}(0.01M)|\mathrm{Ag}(s)$the cell potential is found to be $0.43V$ at $298K$. The magnitude of standard electrode potential for ${\mathrm{Cu}}^{2+}|\mathrm{Cu}$ is____$\times {10}^{-2}V$ $[\mathrm{Given}:{E}_{{\mathrm{Ag}}^{+}/\mathrm{Ag}}^{\Theta }=0.80V\mathrm{and}\frac{2.303\mathrm{RT}}{F}=0.06V]$

The solubility product of a sparingly soluble salt ${A}_{2}{X}_{3}$ is $1.1\times {10}^{-23}$. If specific conductance of the solution is $3\times {10}^{-5}{\mathrm{Sm}}^{-1}$, the limiting molar conductivity of the solution is $x\times {10}^{-3}S{m}^{2}{\mathrm{mol}}^{-1}$. The value of $x$ is

Consider an imaginary ion $X3-2248$. The nucleus contains '$a$'$%$ more neutrons than the number of electrons in the ion. The value of '$a$' is

The depression in freezing point observed for a formic acid solution of concentration $0.5\mathrm{mL}{L}^{-1}$ is $0.0405^{\circ}C$. Density of formic acid is $1.05g{\mathrm{mL}}^{-1}$. The Van't Hoff factor of the formic acid solution is nearly: (Given for water ${k}_{f}=1.86K\mathrm{kg}{\mathrm{mol}}^{-1}$)

For a reaction $A\rightarrow 2B+C$ the half lives are $100s$ and $50s$ when the concentration of reactant $A$ is $0.5$ and $1.0\mathrm{mol}L=$ respectively. The order of the reaction is

$2\mathrm{NO}+2{H}_{2}\rightarrow {N}_{2}+2{H}_{2}O$ The above reaction has been studied at $800^{\circ}C$. The related data are given in the table below <table class="pyq-table"><tbody><tr><td>Reaction serial number</td><td>Initial pressure of${H}_{2}/\mathrm{kPa}$</td><td>Initial Pressure of $\mathrm{NO}/\mathrm{kPa}$</td><td>Initial rate $(\frac{-\mathrm{dp}}{\mathrm{dt}})/(\mathrm{kPa}/s)$</td></tr><tr><td>$1$</td><td>$65.6$</td><td>$40.0$</td><td>$0.135$</td></tr><tr><td>$2$</td><td>$65.6$</td><td>$20.1$</td><td>$0.033$</td></tr><tr><td>$3$</td><td>$38.6$</td><td>$65.6$</td><td>$0.214$</td></tr><tr><td>$4$</td><td>$19.2$</td><td>$65.6$</td><td>$0.106$</td></tr></tbody></table>The order of the reaction with respect to NO is____

$20\mathrm{mL}$ of $0.02{\mathrm{MK}}_{2}{\mathrm{Cr}}_{2}{O}_{7}$ solution is used for the titration of $10\mathrm{mL}$ of ${\mathrm{Fe}}^{2+}$ solution in the acidic medium. The molarity of ${\mathrm{Fe}}^{2+}$ solution is____$\times {10}^{-2}M$

The ${(\frac{\partial E}{\partial T})}_{P}$ of different types of half cells are as follows : $\begin{matrix}A & B & C & D \\ 1\times {10}^{-4} & 2\times {10}^{-4} & 0.1\times {10}^{-4} & 0.2\times {10}^{-4}\end{matrix}$ (Where $E$ is the electromotive force). Which of the above half cells would be preferred to be used as reference electrode

${\mathrm{Ka}}_{1},{\mathrm{Ka}}_{2}$ and ${\mathrm{Ka}}_{3}$ are the respective ionization constants for the following reactions $(a),(b)$ and $(c)$. (a) ${H}_{2}{C}_{2}{O}_{4}\rightleftharpoons {H}^{+}+{\mathrm{HC}}_{2}{O}_{4}^{-}$ (b) ${\mathrm{HC}}_{2}{O}_{4}^{-}\rightleftharpoons {H}^{+}+{\mathrm{HC}}_{2}{O}_{4}^{2-}$ (c) ${H}_{2}{C}_{2}{O}_{4}\rightleftharpoons 2{H}^{+}+{C}_{2}{O}_{4}^{2-}$ The relationship between ${K}_{{a}_{1}},{K}_{{a}_{2}}$ and ${K}_{{a}_{3}}$ is given as