Physical Chemistry PYQ — Page 74

The formation of the oxide ion $\mathrm{O}^{2-}(\mathrm{g})$ requires first an exothermic and then an endothermic step as shown below $\mathrm{O}(\mathrm{g})+\mathrm{e}^{-} \mathrm{O}^{-}(\mathrm{g}) \Delta \mathrm{H}^{\circ}=-142 \mathrm{kJmol}^{-1}$ $\mathrm{O}^{-}(\mathrm{g})+\mathrm{e}^{-} \mathrm{O}^{2-}(\mathrm{g}) \Delta \mathrm{H}^{\circ}=844 \mathrm{kJmol}^{-1}$

The equilibrium constant for the reaction $\mathrm{N}_2(\mathrm{~g})+\mathrm{O}_2(\mathrm{~g}) \rightleftharpoons 2 \mathrm{NO}(\mathrm{g})$ at temperature $\mathrm{T}$ is $4 \times 10^{-4}$. The value of $\mathrm{Kc}$ for the reaction $\mathrm{NO}(\mathrm{g}) \rightleftharpoons \frac{1}{2} \mathrm{~N}_2(\mathrm{~g})+\frac{1}{2} \mathrm{O}_2(\mathrm{~g})$ at the same temperature is

The enthalpies of combustion of carbon and carbon monoxide are $-393.5$ and $-283 \mathrm{~kJ} \mathrm{~mol}^{-1}$ respectively. The enthalpy of formation of carbon monoxide per mole is

The conjugate base of $\mathrm{H}_2 \mathrm{PO}_4^{-}$is

$6.02 \times 10^{20}$ molecules of urea are present in $100 \mathrm{ml}$ of its solution. The concentration of urea solution is

In hydrogen - oxygen fuel cell, combustion of hydrogen occurs to

In first order reaction, the concentration of the reactant decreases from $0.8 \mathrm{M}$ to $0.4 \mathrm{M}$ in 15 minutes. The time taken for the concentration to change from $0.1 \mathrm{M}$ to $0.025 \mathrm{M}$ is

In a cell that utilises the reaction $\mathrm{Zn}(\mathrm{s})+2 \mathrm{H}^{+}(\mathrm{aq}) \longrightarrow \mathrm{Zn}^{2+}(\mathrm{aq})+\mathrm{H}_2(\mathrm{~g})$ addition of $\mathrm{H}_2 \mathrm{SO}_4$ to cathode compartment, will

For the reaction, $\mathrm{CO}(\mathrm{g})+\mathrm{Cl}_2(\mathrm{~g}) \rightleftharpoons \mathrm{COCl}_2(\mathrm{~g})$ the $\frac{\mathrm{K}_{\mathrm{p}}}{\mathrm{K}_{\mathrm{c}}}$ is equal to

Excess of $\mathrm{KI}$ reacts with $\mathrm{CuSO}_4$ solution and then $\mathrm{Na}_2 \mathrm{~S}_2 \mathrm{O}_3$ solution is added to it. Which of the statements is incorrect for this reaction?

Consider the ground state of $\mathrm{Cr}$ atom $(Z=24)$. The number of electrons with the azimuthal quantum numbers $\mathrm{I}=1$ and 2 are respectively

Consider the following $\mathrm{E}^{\circ}$ values $$ \begin{aligned} & \mathrm{E}_{\mathrm{Fe}^{3+} / \mathrm{Fe}^{2+}}^{\circ}=0.77 \mathrm{~V} \\ & \mathrm{E}_{\mathrm{Sn}^{2+} / \mathrm{Sn}}^{\circ}=-0.14 \mathrm{~V} \end{aligned} $$ Under standard conditions the potential for the reaction $\mathrm{Sn}(\mathrm{s})+2 \mathrm{Fe}^{3+}(\mathrm{aq}) \longrightarrow 2 \mathrm{Fe}^{2+}(\mathrm{aq})+\mathrm{Sn}^{2+}(\mathrm{aq})$ is

An ideal gas expands in volume from $1 \times 10^{-3} \mathrm{~m}^3$ to $1 \times 10^{-2} \mathrm{~m}^3$ at $300 \mathrm{~K}$ against a constant pressure of $1 \times 10^5 \mathrm{Nm}^{-2}$. The work done is

Among the properties (a) reducing (b) oxidising (c) complexing, the set of properties shown by $\mathrm{CN}^{-}$ion towards metal species is

Among $\mathrm{Al}_2 \mathrm{O}_3, \mathrm{SiO}_2, \mathrm{P}_2 \mathrm{O}_3$ and $\mathrm{SO}_2$ the correct order of acid strength is

Which one of the following statements is not true?

Which one of the following groupings represents a collection of isoelectronic species? (At. nos,: 55, Br:35)

Which of the following could act as apropellant for rockets?

When rain is accompanied by a thunderstorm, the collected rain water will have a $\mathrm{pH}$ value

When during electrolysis of a solution of $\mathrm{AgNO}_3 9650$ coulombs of charge pass through the electroplating bath, the mass of silver deposited on the cathode will be

What volume of hydrogen gas, at $273 \mathrm{~K}$ and $1 \mathrm{~atm}$, pressure will be consumed in obtaining $21.6 \mathrm{~g}$ of elemental boron (atomic mass $=10.8$ ) from the reducti on of boron trichloride by hydrogen?

The solubility in water of a sparingly soluble salt $\mathrm{AB}$ is $1.0 \times 10^{-5} \mathrm{~mol} \mathrm{~L}^{-1}$. Its solubility product number will be

The rate law for a reaction between the substances $\mathrm{A}$ and $\mathrm{B}$ is given by Rate $=\mathrm{k}[\mathrm{A}]^{\mathrm{n}}[\mathrm{B}]^{\mathrm{m}}$ On doubling the concentration of A and halving the concentration of B, the ratio of the new rate to the earlier rate of the reaction will be as

The orbital angular momentum for an electron revolving in an orbit is given by $\sqrt{l(l+1)} \cdot \frac{\mathrm{h}}{2 \pi}$. This momentum for an s-electron will be given by