Physical Chemistry PYQ — Page 8

A non-volatile, non-electrolyte solid solute when dissolved in $40$ g of a solvent, the vapour pressure of the solvent decreased from $760$ mm Hg to $750$ mm Hg. If the same solution boils at $320$ K, then the number of moles of the solvent present in the solution is _____. (Nearest integer) [Given: boiling point of the pure solvent $= 319.5$ K, $K_b$ of the solvent $= 0.3$ K kg mol$^{-1}$]

The values of pressure equilibrium constant recorded at different temperatures for the following equilibrium reaction have been given below $A(g) \rightleftharpoons B(g) + C(g)$ <table class="pyq-table"><tbody><tr><td>$\dfrac{1}{T}(\text{K}^{-1})$</td><td>$\log_{10} K_p$</td></tr><tr><td>$0.05$</td><td>$3.5$</td></tr><tr><td>$0.06$</td><td>$2.5$</td></tr><tr><td>$0.07$</td><td>$1.5$</td></tr></tbody></table> The magnitude of $\dfrac{\Delta H°}{R}$ calculated from the above data is _____. (Nearest integer)

At $25°C$, $20.0$ mL of $0.2$ M weak monoprotic acid HX is titrated against $0.2$ M NaOH. The pH of the solution (a) at the start of the titration (when NaOH has not been added) and (b) when $10$ mL of NaOH is added respectively, are: Given: $K_a = 5 \times 10^{-4}$, $pK_a = 3.3$, $\alpha << 1$ <table class="pyq-table"><tbody><tr><th>(a)</th><th>(b)</th></tr></tbody></table>

Consider the first order reaction $R \rightarrow P$. The fraction of molecules decomposed in the given first order reaction can be expressed as

Given is a concentrated solution of a weak electrolyte $A_xB_y$ of concentration 'c' and dissociation constant 'K'. The degree of dissociation is given by :

Which of the following graphs between pressure ' p ' versus volume ' V ' represents the maximum work done?

$19.5$ g of fluoro acetic acid (molar mass $= 78$ g mol$^{-1}$) is dissolved in $500$ g of water at $298$ K. The depression in the freezing point of water was $1°$C. What is $K_a$ of fluoro acetic acid? (For water, $K_f = 1.86$ K kg mol$^{-1}$). Assume molarity and molality to have same values.

If the half life of a first order reaction is $6.93$ minutes then the time required for completion of $99$% of the reaction will be _____ minutes. (Given : $\log 2 = 0.3010$)

Consider the following gaseous equilibrium in a closed container of volume ' V ' at $\mathrm{T}(\mathrm{K})$. $\mathrm{P}_{2}(\mathrm{~g})+\mathrm{Q}_{2}(\mathrm{~g}) \rightleftharpoons 2 \mathrm{PQ}(\mathrm{g})$ 2 moles each of $\mathrm{P}_{2}(\mathrm{~g}), \mathrm{Q}_{2}(\mathrm{~g})$ and $\mathrm{PQ}(\mathrm{g})$ are present at equilibrium. Now one mole each of ' $\mathrm{P}_{2}$ ' and ' $\mathrm{Q}_{2}$ ' are added to the equilibrium keeping the temperature at $\mathrm{T}(\mathrm{K})$. The number of moles of $P_{2}, Q_{2}$ and $P Q$ at the new equilibrium, respectively, are

$500$ mL of $0.2$ M MnO$_4^-$ solution in basic medium when mixed with $500$ mL of $1.5$ M KI solution, oxidises iodide ions to liberate molecular iodine. This liberated iodine is then titrated with a standard $x$ M thiosulphate solution in presence of starch till the end point. If $300$ mL of thiosulphate was consumed, then the value of $x$ is __________.

 Consider the above electrochemical cell where a metal electrode (M) is undergoing redox reaction by forming $\mathrm{M}^{+}\left(\mathrm{M} \rightarrow \mathrm{M}^{+}+\mathrm{e}^{-}\right)$. The cation $\mathrm{M}^{+}$is present in two different concentrations $c_{1}$ and $c_{2}$ as shown above. Which of the following statement is correct for generating a positive cell potential?

The Bohr radius of a hydrogen like species is $70.53$ pm. The species and the stationary state $(n)$ are respectively (Given : Hydrogen atom Bohr radius is $52.9$ pm)

The correct order of total number of atoms present in<br>(A) $2$ moles of cyclohexane<br>(B) $684$ g of sucrose<br>(C) $90.8$ L of dihydrogen at STP<br>is:

Liquid A and B form an ideal solution. The vapour pressure of pure liquids A and B are 350 and 750 mm Hg respectively at the same temperature. If $\mathrm{x}_{\mathrm{A}}$ and $x_B$ are the mole fraction of $A$ and $B$ in solution while $y_A$ and $y_B$ are the mole fraction of A and B in vapour phase then :

On combustion 0.210 g of an orgainc compound containing $\mathrm{C}, \mathrm{H}$ and O gave $0.127 \mathrm{~g} \mathrm{H}_2 \mathrm{O}$ and 0.307 $\mathrm{g} \mathrm{CO}_2$. The percentages of hydrogen and oxygen in the given organic compound respectively are:

Which of the following properties will change when system containing solution 1 will become solution 2? 

Let us consider an endothermic reaction which is non-spontaneous at the freezing point of water. However, the reaction is spontaneous at boiling point of water. Choose the correct option.

Compounds that should not be used as primary standards in titrimetric analysis are : A. $\mathrm{Na}_2 \mathrm{Cr}_2 \mathrm{O}_7$ B. Oxalic acid C. NaOH D. $\mathrm{FeSO}_4 \cdot 6 \mathrm{H}_2 \mathrm{O}$ E. Sodium tetraborate Choose the most appropriate answer from the options given below:

A sample of n-octane $(1.14 \mathrm{~g})$ was completely burnt in excess of oxygen in a bomb calorimeter, whose heat capacity is $5 \mathrm{~kJ} \mathrm{~K}^{-1}$. As a result of combustion reaction, the temperature of the calorimeter is increased by 5 K. The magnitude of the heat of combustion of octane at constant volume is ______ $\mathrm{kJ} \mathrm{mol}^{-1}$ (nearest integer).

Consider the following electrochemical cell at standard condition. \(\begin{aligned} & \mathrm{Au}(\mathrm{s})\left|\mathrm{QH}_2, \mathrm{Q}\right| \mathrm{NH}_4 \mathrm{X}(0.01 \mathrm{M})| | \mathrm{Ag}^{+}(1 \mathrm{M}) \mid \mathrm{Ag}(\mathrm{s}) \\ & \mathrm{E}_{\text {cell }}=+0.4 \mathrm{~V} \end{aligned}\) The couple \(\mathrm{QH}_2 / \mathrm{Q}\) represents quinhydrone electrode, the half cell reaction is given below  The \(\mathrm{pK}_{\mathrm{b}}\) value of the ammonium halide salt \(\left(\mathrm{NH}_4 \mathrm{X}\right)\) used here is _________. (nearest integer)

A liquid when kept inside a thermally insulated closed vessel at $25^{\circ} \mathrm{C}$ was mechanically stirred from outside. What will be the correct option for the following thermodynamic parameters ?

$\mathrm{K}_{\text {sp }}$ for $\mathrm{Cr}(\mathrm{OH})_3$ is $1.6 \times 10^{-30}$. What is the molar solubility of this salt in water?

Consider the given figure and choose the correct option : 

On complete combustion 1.0 g of an organic compound (X) gave 1.46 g of \(\mathrm{CO}_2\) and 0.567 g of \(\mathrm{H}_2 \mathrm{O}\). The empirical formula mass of compound \((\mathrm{X})\) is ________ g. (Given molar mass in \(\mathrm{g} \mathrm{mol}^{-1} \mathrm{C}: 12, \mathrm{H}: 1, \mathrm{O}: 16\))