Physical Chemistry PYQ — Page 68

$5 \mathrm{~g}$ of benzene on nitration gave $6.6 \mathrm{~g}$ of nitrobenzene. The theoretical yield of the nitrobenzene will be

One mole of an ideal gas is expanded isothermally and reversibly to half of its initial pressure. $\Delta S$ for the process in $\mathrm{J} \mathrm{K}^{-1} \mathrm{~mol}^{-1}$ is $[\ln 2=0.693$ and $R=8.314, \mathrm{~J} /(\mathrm{mol} \mathrm{K})]$

In a chemical reaction $A$ is converted into $B$. The rates of reaction, starting with initial concentrations of $A$ as $2 \times 10^{-3} \mathrm{M}$ and $1 \times 10^{-3}$ $\mathrm{M}$, are equal to $2.40 \times 10^{-4} \mathrm{Ms}^{-1}$ and $0.60 \times 10^{-4} \mathrm{Ms}^{-1}$ respectively. The order of reaction with respect to reactant $A$ will be

Given $$ \mathrm{E}_{\mathrm{Cu}^{2+} / \mathrm{Cu}}^{\circ}=0.34 \mathrm{~V}, \mathrm{E}_{\mathrm{Cu}^{2+} / \mathrm{Cu}}^{\circ}=0.15 \mathrm{~V} $$ Standard electrode potential for the half cell $\mathrm{Cu}^{+} / \mathrm{Cu}$ is

For a first order reaction, $(A) \rightarrow$ products, the concentration of $A$ changes from $0.1 \mathrm{~M}$ to $0.025 \mathrm{~M}$ in $40$ minutes. The rate of reaction when the concentration of $A$ is $0.01 \mathrm{~M}$ is :

Liquids A and B form an ideal solution. At $30^{\circ} \mathrm{C}$, the total vapour pressure of a solution containing $1 \mathrm{~mol}$ of A and $2 \mathrm{~mol}$ of B is $250 \mathrm{~mm} \mathrm{Hg}$. The total vapour pressure becomes $300 \mathrm{~mm} \mathrm{Hg}$ when 1 more mol of $\mathrm{A}$ is added to the first solution. The vapour pressures of pure $\mathrm{A}$ and $\mathrm{B}$ at the same temperature are

Given (i) $\operatorname{HCN}(a q)+\mathrm{H}_2 \mathrm{O}(b) \rightleftharpoons \mathrm{H}_3 \mathrm{O}^{+}(a q)+\mathrm{CN}^{-}(a q)$ $K_{\mathrm{a}}=6.2 \times 10^{-10}$ (ii) $\mathrm{CN}^{-}(a q)+\mathrm{H}_2 \mathrm{O}(\mathrm{l}) \rightleftharpoons \mathrm{HCN}(a q)+\mathrm{OH}^{-}(a q)$ $K_{\mathrm{b}}=1.6 \times 10^{-5}$. These equilibria show the following order of the relative base strength,

$K_1, K_2$ and $K_3$ are the equilibrium constants of the following reactions (I), (II) and (III) respectively: (I) $\mathrm{N}_2+2 \mathrm{O}_2 \rightleftharpoons 2 \mathrm{NO}_2$ (II) $2 \mathrm{NO}_2 \rightleftharpoons \mathrm{N}_2+2 \mathrm{O}_2$ (III) $\mathrm{NO}_2 \rightleftharpoons \frac{1}{2} \mathrm{~N}_2+\mathrm{O}_2$ The correct relation from the following is

The activation energy for a reaction which doubles the rate when the temperature is raised from $298 \mathrm{~K}$ to $308 \mathrm{~K}$ is

A battery is constructed of $\mathrm{Cr}$ and $\mathrm{Na}_2 \mathrm{Cr}_2 \mathrm{O}_7$. The unbalanced chemical equation when such a battery discharges is following: $$ \mathrm{Na}_2 \mathrm{Cr}_2 \mathrm{O}_7+\mathrm{Cr}+\mathrm{H}^{+} \rightarrow \mathrm{Cr}^{3+}+\mathrm{H}_2 \mathrm{O}+\mathrm{Na}^{+} $$ If one Faraday of electricity is passed through the battery during the charging, the number of moles of $\mathrm{Cr}^{3+}$ removed from the solution is

The freezing point of a $1.00 \mathrm{~m}$ aqueous solution of $\mathrm{HF}$ is found to be $-1.91^{\circ} \mathrm{C}$. The freezing point constant of water, $K_f$ is $1.86 \mathrm{~K} \mathrm{~kg} \mathrm{~mol}^{-1}$. The percentage dissociation of $\mathrm{HF}$ at this concentration is

The value of $K_p$ for the equilibrium reaction $\mathrm{N}_2 \mathrm{O}_4(g) \rightleftharpoons 2 \mathrm{NO}_2(g)$ is 2 . The percentage dissociation of $\mathrm{N}_2 \mathrm{O}_4(g)$ at a pressure of $0.5 \mathrm{~atm}$ is

The equilibrium constant $\left(\mathrm{K}_{\mathrm{c}}\right)$ for the reaction $\mathrm{N}_2(\mathrm{g})+\mathrm{O}_2(\mathrm{~g}) \rightarrow 2 \mathrm{NO}(\mathrm{g})$ at temperature $\mathrm{T}$ is $4 \times 10^{-4}$. The value of $\mathrm{K}_{\mathrm{c}}$ for the reaction, $\mathrm{NO}(\mathrm{g}) \rightarrow{1 / 2} \mathrm{~N}_2(\mathrm{g})+{1 / 2} \mathrm{~O}_2(\mathrm{g})$ at the same temperature is :

The concentrated sulphuric acid that is peddled commercial is $95 \% \mathrm{H}_2 \mathrm{SO}_4$ by weight. If the density of this commercial acid is $1.834 \mathrm{~g} \mathrm{~cm}^{-3}$, the molarity of this solution is

The enthalpy of neutralisation of $\mathrm{NH}_4 \mathrm{OH}$ with $\mathrm{HCl}$ is $-51.46 \mathrm{~kJ} \mathrm{~mol}^{-1}$ and the enthalpy of neutralisation of $\mathrm{NaOH}$ with $\mathrm{HCl}$ is $-55.90 \mathrm{~kJ} \mathrm{~mol}^{-1}$. The enthalpy of ionisation of $\mathrm{NH}_4 \mathrm{OH}$ is

The standard reduction potentials for $\mathrm{Zn}^{2+} / \mathrm{Zn}, \mathrm{Ni}^{2+} / \mathrm{Ni}$, and $\mathrm{Fe}^{2+} / \mathrm{Fe}$ are $-0.76,-0.23$ and $-0.44 \mathrm{~V}$ respectively. The reaction $\mathrm{X}+\mathrm{Y}^{2+} \rightarrow \mathrm{X}^{2+}+\mathrm{Y}$ will be spontaneous when:

The ppm level of $\mathrm{F}^{-}$in a $500 \mathrm{~g}$ sample of a tooth paste containing $0.2 \mathrm{~g} \mathrm{~F}^{-}$is

$\mathrm{K}_{\mathrm{f}}$ for water is $1.86 \mathrm{~K} \mathrm{~kg} \mathrm{~mol}^{-1}$. If your automobile radiator holds $1.0 \mathrm{~kg}$ of water, how many grams of ethylene glycol $\left(\mathrm{C}_2 \mathrm{H}_6 \mathrm{O}_2\right)$ must you add to get the freezing point of the solution lowered to $-2.8^{\circ} \mathrm{C}$ ?

When $\mathrm{CO}_{2(\mathrm{~g})}$ is passed over red hot coke it partially gets reduced to $\mathrm{CO}(g)$. Upon passing $0.5 \mathrm{~L}$ of $\mathrm{CO}_2(g)$ over red hot coke, the total volume of the gases increased to $700 \mathrm{~mL}$. The composition of the gaseous mixture at STP is

The difference between the reaction enthalpy change $\left(\Delta_{\mathrm{r}} \mathrm{H}\right)$ and reaction internal energy change $\left(\Delta_{\mathrm{r}} \mathrm{U}\right)$ for the reaction: $$ 2 \mathrm{C}_6 \mathrm{H}_6(\mathrm{l})+15 \mathrm{O}_2(\mathrm{~g}) \longrightarrow $$ at $300 \mathrm{~K}$ is $\left(\mathrm{R}=8.314 \mathrm{~J} \mathrm{~mol}^{-1} \mathrm{~K}^{-1}\right)$

The solubility of $\mathrm{PbI}_2$ at $25^{\circ} \mathrm{C}$ is $0.7 \mathrm{~g} \mathrm{~L}^{-1}$. The solubility product of $\mathrm{PbI}_2$ at this temperature is (molar mass of $\mathrm{PbI}_2=461.2 \mathrm{~g} \mathrm{~mol}^{-1}$ )

If $K_{s p}$ of $\mathrm{CaF}_2$ at $25^{\circ} \mathrm{C}$ is $1.7 \times 10^{-10}$, the combination amongst the following which gives a precipitate of $\mathrm{CaF}_2$ is

The standard potentials of $\mathrm{Ag}^{+} / \mathrm{Ag}, \mathrm{Hg}_2{ }^{2+} / 2 \mathrm{Hg}$, $\mathrm{Cu}^{2+} / \mathrm{Cu}$ and $\mathrm{Mg}^{2+} / \mathrm{Mg}$ electrodes are $0.80,0.79$, $0.34$ and $-2.37 \mathrm{~V}$, respectively. An aqueous solution which contains one mole per litre of the salts of each of the four metals is electrolyzed. With increasing voltage, the correct sequence of deposition of the metals at the cathode is

If the radius of first orbit of $\mathrm{H}$ atom is $a_0$, the deBroglie wavelength of an electron in the third orbit is