Physical Chemistry PYQ — Page 15

Which has the maximum number of molecules among the following?

A 0.1 molal aqueous solution of a weak acid is $30 \%$ ionised. If $K_f$ for water is $1.86^{\circ} \mathrm{C} / \mathrm{m}$, the freezing point of the solution will be

A gaseous mixture was prepared by taking equal moles of $\mathrm{CO}$ and $\mathrm{N}_2$. If the total pressure of the mixture was found 1 atmosphere, the partial pressure of the nitrogen $\left(\mathrm{N}_2\right)$ in the mixture is

If the enthalpy change for the transition of liquid water to steam is $30 \mathrm{~kJ} \mathrm{~mol}^{-1}$ at $27^{\circ} \mathrm{C}$, the entropy change for the process would be

In qualitative analysis, the metals of group I can be separated from other ions by precipitating them as chloride salts. A solution initially contains $\mathrm{Ag}^{+}$and $\mathrm{Pb}^{2+}$ at a concentration of $0.10 \mathrm{M}$. Aqueous $\mathrm{HCl}$ is added to this solution until the $\mathrm{Cl}^{-}$concentration is $0.10 \mathrm{M}$. What will be the concentration of $\mathrm{Ag}^{+}$and $\mathrm{Pb}^{2+}$ be at equilibrium? ( $K_{\mathrm{sp}}$ for $\mathrm{AgCl}=1.8 \times 10^{-10}, K_{\mathrm{sp}}$ for $\mathrm{PbCl}_2=1.7 \times 10^{-5}$ )

Two gases $A$ and $B$ having the same volume diffuse through a porous partition in 20 and 10 seconds respectively. The molecular mass of $A$ is $49 \mathrm{u}$. Molecular mass of $B$ will be

The half-life of a substance in a certain enzyme-catalysed reaction is $138 \mathrm{~s}$. The time required for the concentration of the substance to fall from $1.28 \mathrm{mg} \mathrm{L}^{-1}$ to $0.04 \mathrm{mg} \mathrm{L}^{-1}$ is

According to the Bohr theory, which of the following transitions in the hydrogen atom will give rise to the least energetic photon?

$200 \mathrm{~mL}$ of an aqueous solution of a protein contains its $1.26 \mathrm{~g}$. The osmotic pressure of this solution at $300 \mathrm{~K}$ is found to be $2.57 \times 10^{-3}$ bar. The molar mass of protein will be

Standard electrode potential for $\mathrm{Sn}^{4+} / \mathrm{Sn}^{2+}$ couple is $+0.15 \mathrm{~V}$ and that for the $\mathrm{Cr}^{3+} / \mathrm{Cr}$ couple is -0.74 . These two couples in their standard state are connected to make a cell. The cell potential will be

For the reaction, \(\mathrm{N}_2(\mathrm{~g})+\mathrm{O}_2(\mathrm{~g}) \rightleftharpoons 2 \mathrm{NO}(\mathrm{g})\), the equilibrium constant is \(\mathrm{K}_1\). The equilibrium constant is \(\mathrm{K}_2\) for \(2 \mathrm{NO}(\mathrm{g})+\mathrm{O}_2(\mathrm{~g}) \rightleftharpoons 2 \mathrm{NO}_2(\mathrm{~g})\). What is K for the reaction \(\mathrm{NO}_2(\mathrm{~g}) \rightleftharpoons \frac{1}{2} \mathrm{~N}_2(\mathrm{~g})+\mathrm{O}_2(\mathrm{~g}) ?\)

Mole fraction of the solute in a 1.00 molal aqueous solution is

A buffer solution is prepared in which the concentration of $\mathrm{NH}_3$ is $0.30 \mathrm{M}$ and the concentration of $\mathrm{NH}_4^{+}$is $0.20 \mathrm{M}$. If the equilibrium constant, $K_b$ for $\mathrm{NH}_3$ equals $1.8 \times 10^{-5}$, what is the $\mathrm{pH}$ of this solution? $(\log 2.7=0.43)$

The unit of rate constant for a zero order reaction is

The energies $E_1$ and $E_2$ of two radiations are $25 \mathrm{eV}$ and $50 \mathrm{eV}$ respectively. The relation between their wavelengths i.e., $\lambda_1$ and $\lambda_2$ will be

A solution contains $\mathrm{Fe}^{2+}, \mathrm{Fe}^{3+}$ and $\mathrm{I}^{-}$ions. This solution was treated with iodine at $35^{\circ} \mathrm{C}$. $E^{\circ}$ for $\mathrm{Fe}^{3+} / \mathrm{Fe}^{2+}$ is $+0.77 \mathrm{~V}$ and $\mathrm{E}^{\circ}$ for $\mathrm{I}_2 / 2 \mathrm{I}^{-}=0.536 \mathrm{~V}$. The favourable redox reaction is

Standard electrode potential of three metals $X, Y$ and $Z$ are $-1.2 \mathrm{~V},+0.5 \mathrm{~V}$ and $-3.0 \mathrm{~V}$ respectively. The reducing power of these metals will be

The rate of reaction $2 \mathrm{~N}_2 \mathrm{O}_5 \longrightarrow 4 \mathrm{NO}_2+\mathrm{O}_2$ can be written in three ways $\begin{aligned} \frac{-d\left[\mathrm{~N}_2 \mathrm{O}_5\right]}{d t} & =k\left[\mathrm{~N}_2 \mathrm{O}_5\right] \\ \frac{d\left[\mathrm{NO}_2\right]}{d t} & =k^{\prime}\left[\mathrm{N}_2 \mathrm{O}_5\right] \\ \frac{d\left[\mathrm{O}_2\right]}{d t} & =k^{\prime \prime}\left[\mathrm{N}_2 \mathrm{O}_5\right] \end{aligned}$ The relationship between $k$ and $k^{\prime}$ and between $k$ and $k^{\prime \prime}$ are

Which of the following expressions correctly represents the equivalent conductance at infinite dilution of $\mathrm{Al}_2\left(\mathrm{SO}_4\right)_3$. Given that $\Lambda_{\mathrm{Al}^{3+}}^{\circ}$ and $\Lambda_{\mathrm{SO}_4^{2-}}^{\circ}$ are the equivalent conductances at infinite dilution of the respective ions?

During the kinetic study of the reaction, $2 \mathrm{~A}+\mathrm{B} \rightarrow \mathrm{C}+\mathrm{D}$, following results were obtained \(\begin{array}{|c|c|c|c|} \hline \text { Run } & [A] / \mathrm{mol~} \mathrm{L}^{-1} & [B] / \mathrm{mol~} \mathrm{L}^{-1} & \begin{array}{cc} \text{Initial rate of} \\ \text{formation of} \\ D / \mathrm{mol~} \mathrm{L}^{-1} \mathrm{~min}^{-1} \end{array} \\ \hline \text { I } & 0.1 & 0.1 & 6.0 \times 10^{-3} \\ \hline \text { II } & 0.3 & 0.2 & 7.2 \times 10^{-2} \\ \hline \text { III } & 0.3 & 0.4 & 2.88 \times 10^{-1} \\ \hline \text { IV } & 0.4 & 0.1 & 2.40 \times 10^{-2} \\ \hline \end{array}\) Based on the above data which one of the following is correct?

The rate of the reaction, $2 \mathrm{NO}+\mathrm{Cl}_2 \longrightarrow 2 \mathrm{NOCl}$ is given by the rate equation, rate $=\mathrm{k}[\mathrm{NO}]^2\left[\mathrm{Cl}_2\right]$ The value of the rate constant can be increased by

The following two reactions are known $$ \begin{aligned} & \mathrm{Fe}_2 \mathrm{O}_3(\mathrm{~s})+3 \mathrm{CO}(\mathrm{g}) \longrightarrow 2 \mathrm{Fe}(\mathrm{s})+3 \mathrm{CO}_2(\mathrm{~g}), \\ & \Delta \mathrm{H}=-26.8 \mathrm{~kJ} \\ & \mathrm{FeO}(\mathrm{s})+\mathrm{CO}(\mathrm{g}) \longrightarrow \mathrm{Fe}(\mathrm{s})+\mathrm{CO}_2(\mathrm{~g}) \\ & \Delta \mathrm{H}=-16.5 \mathrm{~kJ} \end{aligned} $$ The value of $\Delta \mathrm{H}$ for the following reaction $\mathrm{Fe}_2 \mathrm{O}_3(\mathrm{~s})+\mathrm{CO}(\mathrm{g}) \longrightarrow 2 \mathrm{FeO}(\mathrm{s})+\mathrm{CO}_2(\mathrm{~g})$ is

If $\mathrm{pH}$ of a saturated solution of $\mathrm{Ba}(\mathrm{OH})_2$ is 12 , the value of its $K_{s p}$ is

An aqueous solution is 1.00 molal in KI. Which change will cause the vapour pressure of the solution to increase ?