Physical Chemistry PYQ — Page 65

Consider the reaction : ${\text{H}}_{2} {\text{SO}}_{ 3 ( \text{aq} ) } + {\text{Sn}}_{( \text{aq} )}^{ 4 + } + {\text{H}}_{2} {\text{O}}_{( l⁡ )} \rightarrow {\text{Sn}}_{( \text{aq} )}^{ 2 + } + {\text{HSO}}_{ 4 ( \text{aq} ) }^{-} + 3 {\text{H}}_{( \text{aq} )}^{+}$ Which of the following statements is correct ?

Consider the following equilibrium $$ \mathrm{AgCl} \downarrow+2 \mathrm{NH}_3 \rightleftharpoons\left[\mathrm{Ag}\left(\mathrm{NH}_3 2_2\right]^{+}+\mathrm{Cl}^{-}\right. $$ White precipitate of $\mathrm{AgCl}$ appears on adding which of the following?

Consider separate solutions of $0.500M{C}_{2}{H}_{5}\mathrm{OH}(\mathrm{aq}),0.100M{\mathrm{Mg}}_{3}{({\mathrm{PO}}_{4})}_{2}(\mathrm{aq}),0.250M\mathrm{KBr}(\mathrm{aq})$ and $0.125M{\mathrm{Na}}_{3}{\mathrm{PO}}_{4}(\mathrm{aq})$ at $25^{\circ}C$. Which statement is true about these solutions, assuming all salts to be strong electrolytes?

Choose the correct statement with respect to the vapour pressure of a liquid among the following :

Based on the equation: $$ \Delta \mathrm{E}=-2.0 \times 10^{-18} \mathrm{~J}\left(\frac{1}{\mathrm{n}_2^2}-\frac{1}{\mathrm{n}_1^2}\right) $$ the wavelength of the light that must be absorbed to excite hydrogen electron from level $n=1$ to level $\mathrm{n}=2$ will be: $\left(\mathrm{h}=6.625 \times 10^{-34} \mathrm{Js}, \mathrm{C}=3 \times 10^8 \mathrm{~ms}^{-1}\right)$

At a certain temperature, only 50% HI is dissociated into H$_{2}$ and I$_{2}$ at equilibrium. The equilibrium constant is :

Assuming that the degree of hydrolysis is small, the $\mathrm{pH}$ of $0.1 \mathrm{M}$ solution of sodium acetate $\left(\mathrm{K}_{\mathrm{a}}=1.0 \times 10^{-5}\right)$ will be:

A gaseous compound of nitrogen and hydrogen contains $12.5 \%$ (by mass) of hydrogen. The density of the compound relative to hydrogen is 16. The molecular formula of the compound is:

A current of $10.0A$ flows for $2.00h$ through an electrolytic cell containing a molten salt of metal $X$. This results in the decomposition of $0.250\mathrm{mol}$ of metal $X$ at the cathode. The oxidation state of $X$ in the molten salt is: $(F=96,500C)$

Which one of the following arrangements represents the correct order of solubilities of sparingly soluble salts $\mathrm{Hg}_2 \mathrm{Cl}_2, \mathrm{Cr}_2\left(\mathrm{SO}_4\right)_3$, $\mathrm{BaSO}_4$ and $\mathrm{CrCl}_3$ respectively?

Which one of the following arrangements represents the correct order of the proton affinity of the given species :

Which of the following statements/relationships is not correct in thermodynamic changes ?

What would be the $\mathrm{pH}$ of a solution obtained by mixing $5 \mathrm{~g}$ of acetic acid and $7.5 \mathrm{~g}$ of sodium acetate and making the volume equal to $500 \mathrm{~mL}$ ? $\left(\mathrm{K}_{\mathrm{a}}=1.75 \times 10^{-5}, \mathrm{pK}_{\mathrm{a}}=4.76\right)$

What is the $\mathrm{pH}$ of a $10^{-4} \mathrm{M} \mathrm{OH}^{-}$solution at $330 \mathrm{~K}$, if $\mathrm{K}_{\mathrm{w}}$ at $330 \mathrm{~K}$ is $10^{-13.6}$ ?

Vapour pressure of pure benzene is 119 torr and that of toluene is $37.0$ torr at the same temperature. Mole fraction of toluene in vapour phase which is in equilibrium with a solution of benzene and toluene having a mole fraction of toluene $0.50$, will be :

Values of dissociation constant, $K_a$ are given as follows : $\begin{array}{lc}\text { Acid } & \boldsymbol{K}_{\boldsymbol{a}} \\ \mathrm{HCN} & 6.2 \times 10^{-10} \\ \mathrm{HF} & 7.2 \times 10^{-4} \\ \mathrm{HNO}_2 & 4.0 \times 10^{-4}\end{array}$ Correct order of increasing base strength of the base $\mathrm{CN}^{-}, \mathrm{F}^{-}$and $\mathrm{NO}_2^{-}$will be :

The wave number of the first emission line in the Balmer series of $\mathrm{H}$-Spectrum is : $(\mathrm{R}=$ Rydberg constant $)$ :

The reaction $\mathrm{X} \rightarrow \mathrm{Y}$ is an exothermic reaction. Activation energy of the reaction for $\mathrm{X}$ into $\mathrm{Y}$ is $150 \mathrm{~kJ} \mathrm{~mol}^{-1}$. Enthalpy of reaction is $135 \mathrm{~kJ}$ $\mathrm{mol}^{-1}$. The activation energy for the reverse reaction, $\mathrm{Y} \rightarrow \mathrm{X}$ will be :

The ratio $\frac{K_p}{K_c}$ for the reaction $\mathrm{CO}(g)+\frac{1}{2} O_2(g) \rightleftharpoons C O_2(g)$ is:

The rate of a reaction doubles when its temperature changes from $300K\mathrm{to}310K$. Activation energy of such a reaction will be: $(\text{R}={\text{8.314 JK}}^{-1}{mol}^{-1}\mathrm{and}log 2=\text{0.301})$

The rate constant of a zero order reaction is $2.0 \times$ $10^{-2} \mathrm{~mol} \mathrm{~L}^{-1} \mathrm{~s}^{-1}$. If the concentration of the reactant after 25 seconds is $0.5 \mathrm{M}$. What is the initial concentration?

The molarity of a solution obtained by mixing $750\mathrm{mL}$ of $0.5(M)\mathrm{HCl}$ with $250\mathrm{mL}$ of $2(M)\mathrm{HCl}$ will be

The instantaneous rate of disappearance of $\mathrm{MnO}_4^{-}$ion in the following reaction is $4.56 \times 10^{-3} \mathrm{Ms}^{-1}$ $2 \mathrm{MnO}_4^{-}+10 \mathrm{I}^{-}+16 \mathrm{H}^{+} \rightarrow 2 \mathrm{Mn}^{2+}+5 \mathrm{I}_2+8 \mathrm{H}_2 \mathrm{O}$ The rate of appearance $\mathrm{I}_2$ is :

The Gibbs energy for the decomposition of $\mathrm{Al}_2 \mathrm{O}_3$ at $500 \mathrm{~C}$ is as follows : $\frac{2}{3} \mathrm{Al}_2 \mathrm{O}_3 \rightarrow \frac{4}{3} \mathrm{Al}+\mathrm{O}_2, \Delta_r G=+940 \mathrm{~kJ} \mathrm{~mol}^{-1}$ The potential difference needed for the electrolytic reduction of aluminium oxide at $500^{\circ} \mathrm{C}$ should be at least :