Physical Chemistry PYQ — Page 60

Which of the following is a Lewis acid?

An aqueous solution contains an unknown concentration of ${\mathrm{Ba}}^{2+}$. When $50\mathrm{mL}\mathrm{of}a1M$ solution of ${\mathrm{Na}}_{2}{\mathrm{SO}}_{4}$ is added, ${\mathrm{BaSO}}_{4}$ just begins to precipitate. The final volume is $500\mathrm{mL}$. The solubility product of ${\mathrm{BaSO}}_{4}$ is $1\times {10}^{-10}$. What is the original concentration of ${\mathrm{Ba}}^{2+}$?

At 320 K, a gas ${A}_{2}$ is 20 % dissociated to $A(g)$ . The standard Gibbs free energy change at $320 K and 1 atm in J mo{l}^{–1}$ is approximately: $(R = 8.314 {\mathrm{JK}}^{–1} {\mathrm{mol}}^{–1} ;\mathrm{ln}2 = 0.693 ;\mathrm{ln}3 = 1.098)$

When an electric current is passed through acidified water, 112 mL of hydrogen gas at N.T.P was collected at the cathode in 965 seconds. The current passed, in ampere, is:

The mass of a non-volatile, non-electrolyte solute (molar mass $= 50 g {\mathrm{mol}}^{-1}$) needed to be dissolved in 114 g octane to reduce its vapour pressure by 75 %, is:

At ${518}^{o}C,$ the rate of decomposition of a sample of gaseous acetaldehyde, initially at a pressure of $363 \mathrm{Torr}$ was $1.00 \mathrm{Torr} {s}^{-1}$ when $5%$ had reacted and $0.50 \mathrm{Torr} {s}^{-1}$ when 33% had reacted. The order of the reaction is:

When 9.65 ampere current was passed for 1.0 hour into nitrobenzene in acidic medium, the amount of p-aminophenol produced is:

${ \text{pK}}_{\text{a}}$ of a weak acid $( \text{HA})$ and ${ \text{pK}}_{\text{b}}$ of a weak base $( \text{BOH})$ are $3.2$ and $3.4$ respectively. The $\text{pH}$ of their salt $( \text{AB})$ solution at ${ \text{25}}^{\text{o}} \text{C}$ is

The enthalpy change on freezing of $1\mathrm{mol}$ of water at $5^{\circ}C$ to ice at $-5^{\circ}C$ is: (Given ${\Delta }_{\mathrm{fus}} H=6 \mathrm{kJ} {\mathrm{mol}}^{-1}$ at $0^{\circ}C,$ ${C}_{p}({H}_{2}O, l)=75.3 J {\mathrm{mol}}^{-1}{K}^{-1}$ ${C}_{p}({H}_{2}O, s)=36.8 J {\mathrm{mol}}^{-1}{K}^{-1}$ )

Addition of sodium hydroxide solution to a weak acid (HA) results in a buffer of pH 6. If ionization constant of HA is ${10}^{-5}$, the ratio of salt to acid concentration in the buffer solution will be:

A gas undergoes change from state $A$ to state $B$. In this process, the heat absorbed and work done by the gas is $5J\text{and}8J$, respectively. Now gas is brought back to $A$ by another process during which $3J$ of heat is evolved. In this reverse process of $B\mathrm{to}A$.

Given: $C(\mathrm{graphite})+{O}_{2}(g)\rightarrow {\mathrm{CO}}_{2}(g) ;{\Delta }_{r}{H}^{o}=-393.5\mathrm{kJ}{\mathrm{mol}}^{-1}$ ${H}_{2}(g)+\frac{1}{2}{O}_{2}(g)\rightarrow {H}_{2}O(l);{\Delta }_{r}{H}^{o}=-285.8 \mathrm{kJ} {\mathrm{mol}}^{-1}$ ${\mathrm{CO}}_{2}(g)+2{H}_{2}O(l)\rightarrow {\mathrm{CH}}_{4}(g)+2{O}_{2}(g);{\Delta }_{r}{H}^{o}=+890.3 \mathrm{kJ} {\mathrm{mol}}^{-1}$ Based on the above thermochemical equations, the value of ${\Delta }_{r}{H}^{o}$ at $298K$ for the reaction $C(\mathrm{graphite})+2{H}_{2}(g)\rightarrow {\mathrm{CH}}_{4}(g)$ will be:

The most abundant elements by mass in the body of a healthy human adult are: Oxygen (61.4%); Carbon (22.9%), Hydrogen (10.0%); and Nitrogen (2.6%). The weight which a 75kg person would gain if all ${ }^{1}H$ atoms are replaced by ${ }^{2}H$ atoms is:

Among the following species which option contains all isoelectronic species?

If the shortest wavelength in Lyman series of hydrogen atom is $A$, then the longest wavelength in Paschen series of ${\mathrm{He}}^{+}$ is

Consider the following standard electrode potentials (${\text{E}}^{\text{o}}$ in volts) in aqueous solution: $\begin{matrix}\underset{}{\text{E}\text{l}\text{e}\text{m}\text{e}\text{n}\text{t}} & \underset{}{{\text{M}}^{3+}/\text{M}} & \underset{}{{\text{M}}^{+}/\text{M}} \\ \text{A}\text{l} & -1.66 & +0.55 \\ \text{T}\text{l} & +1.26 & -0.34\end{matrix}$ Based on these data, which of the following statements is correct?

Which of the following ions does not liberate hydrogen gas on reaction with dilute acids?

The pair of compounds having metals in their highest oxidation state is

$\text{Δ}\text{U}$ is equal to:

$5g$ of ${\mathrm{Na}}_{2}{\mathrm{SO}}_{4}$ was dissolved in $x g$ of ${H}_{2}O$ . The change in freezing point was found to be $3{.82}^{o}C$ . If ${\mathrm{Na}}_{2}{\mathrm{SO}}_{4}$ is $81.5%$ ionised, the value of $x$ ( ${K}_{f}$ for water $=1{.86}^{o}C \mathrm{kg} {\mathrm{mol}}^{-1}$ ) is approximately: (molar mass of $S=32 g {\mathrm{mol}}^{-1}$ and that of $\mathrm{Na}=23 g {\mathrm{mol}}^{-1}$ )

Given ${E}_{{\mathrm{Cl}}_{2}/{\mathrm{Cl}}^{-}}^{o}=1.36V, {E}_{{\mathrm{Cr}}^{3+}/\mathrm{Cr}}^{o}= -0.74V$ ${E}_{{\mathrm{Cr}}_{2}{O}_{7}^{2-}/{\mathrm{Cr}}^{3+}}^{o}=1.33V, {E}_{{\mathrm{MnO}}_{4}^{-}/{\mathrm{Mn}}^{2+}}^{o}=1.51V.$ Among the following, the strongest reducing agent is:

The electron in the hydrogen atom undergoes transition from higher orbitals to orbital of radius $211.6\mathrm{pm}$. This transition is associated with

For a reaction, $A(g)\rightarrow A(l);\Delta H=-3\mathrm{RT}.$ The correct statement for the reaction is

An ideal gas undergoes isothermal expansion at constant pressure. During the process: