Chemical & Ionic Equilibrium · JEE Main previous year questions

A student needs to prepare a buffer solution of propanoic acid and its sodium salt with pH 4. The ratio of $\frac{[\mathrm{C}{\mathrm{H}}_3\mathrm{C}{\mathrm{H}}_2\mathrm{CO}{\mathrm{O}}^{-}]}{[\mathrm{C}{\mathrm{H}}_3\mathrm{C}{\mathrm{H}}_2\mathrm{COOH}]}$ required to make buffer is ____. Given : $K_{\mathrm{a}}(\mathrm{C}{\mathrm{H}}_3\mathrm{C}{\mathrm{H}}_2\mathrm{COOH})=1.3\times 10^{-5}$

1. A.0.03
2. B.0.13
3. C.0.23
4. D.0.33

1. A.
2. B.
3. C.
4. D.

On the surface of polar stratospheric clouds, hydrolysis of chlorine nitrate gives A and B while its reaction with $\text{HCl}$ produces B and C. A, B and C are, respectively :

1. A.$\text{HOCl},{\text{HNO}}_3,{\text{Cl}}_2$
2. B.${\text{Cl}}_2,{\text{HNO}}_3,\text{HOCl}$
3. C.${\text{HClO}}_2,{\text{HNO}}_2,\text{HOCl}$
4. D.$\text{HOCl},{\text{HNO}}_2,{\text{Cl}}_2\text{O}$

pH value of 0.001 M NaOH solution is ____________.

For the reaction taking place in the cell : $\text{Pt (s)}|{\text{H}}_2\text{ (g)}|{\text{H}}^{+}\text{(aq)}\parallel {\text{Ag}}^{+}\text{(aq)}|\text{Ag (s)}$ $E_{cell}^{\circ }=+0.5332\text{ V}$. The value of ${\Delta }_f{G}^{\circ }$ is ________ ${\text{kJ mol}}^{-1}$. (in nearest integer)

A 0.5 percent solution of potassium chloride was found to freeze at $-0.24^{\circ }\text{C}$. The percentage dissociation of potassium chloride is ________. (Nearest integer) (Molal depression constant for water is $1.80{\text{ K kg mol}}^{-1}$ and molar mass of KCl is $74.6{\text{ g mol}}^{-1}$)

50 mL of 0.1 M $\mathrm{C}{\mathrm{H}}_3\mathrm{COOH}$ is being titrated against 0.1 M NaOH. When 25 mL of NaOH has been added, the pH of the solution will be ________ $\times 10^{-2}$. (Nearest integer) (Given : $\mathrm{p}{\mathrm{K}}_{\mathrm{a}}(\mathrm{C}{\mathrm{H}}_3\mathrm{COOH})=4.76$) $\log 2=0.30$ $\log 3=0.48$ $\log 5=0.69$ $\log 7=0.84$ $\log 11=1.04$

$40\%$ of $\mathrm{HI}$ undergoes decomposition to ${\mathrm{H}}_2$ and ${\mathrm{I}}_2$ at $300\mathrm{K}$. $\Delta {\mathrm{G}}^{\ominus }$ for this decomposition reaction at one atmosphere pressure is ____ $\mathrm{J}\mathrm{mo}{\mathrm{l}}^{-1}$. [nearest integer] (Use $\mathrm{R}=8.31\mathrm{J}{\mathrm{K}}^{-1}\mathrm{mo}{\mathrm{l}}^{-1}$ ; $\log 2=0.3010$, $\ln 10=2.3$, $\log 3=0.477$)

Number of electron deficient molecules among the following ${\mathrm{PH}}_3$, ${\mathrm{B}}_2{\mathrm{H}}_6$, ${\mathrm{CCl}}_4$, ${\mathrm{NH}}_3$, $\mathrm{LiH}$ and ${\mathrm{BCl}}_3$ is

1. A.$0$
2. B.$1$
3. C.$2$
4. D.$3$

The standard free energy change ($\Delta {\mathrm{G}}^{\circ }$) for $50\%$ dissociation of ${\mathrm{N}}_2{\mathrm{O}}_4$ into ${\mathrm{NO}}_2$ at $27^{\circ }\text{C}$ and $1\text{ atm}$ pressure is $-x{\text{ J mol}}^{-1}$. The value of $x$ is $\underline{}$. (Nearest Integer) [Given : $\mathrm{R}=8.31{\text{ J K}}^{-1}{\text{ mol}}^{-1}$, $\log 1.33=0.1239$, $\ln 10=2.3$]

The ${\mathrm{K}}_{\mathrm{sp}}$ for bismuth sulphide $(\mathrm{B}{\mathrm{i}}_2{\mathrm{S}}_3)$ is $1.08\times 10^{-73}$. The solubility of $\mathrm{B}{\mathrm{i}}_2{\mathrm{S}}_3$ in $\mathrm{mol}{\mathrm{L}}^{-1}$ at $298\mathrm{K}$ is :

1. A.$1.0\times 10^{-15}$
2. B.$2.7\times 10^{-12}$
3. C.$3.2\times 10^{-10}$
4. D.$4.2\times 10^{-8}$

Given below are two statements one is labelled as Assertion A and the other is labelled as Reason R : Assertion A : The amphoteric nature of water is explained by using Lewis acid/base concept. Reason R : Water acts as an acid with $\mathrm{N}{\mathrm{H}}_3$ and as a base with ${\mathrm{H}}_2\mathrm{S}$. In the light of the above statements choose the correct answer from the options given below :

1. A.Both A and R are true and R is the correct explanation of A.
2. B.Both A and R are true but R is NOT the correct explanation of A.
3. C.A is true but R is false.
4. D.A is false but R is true.

${\mathrm{PCl}}_5$ dissociates as ${\mathrm{PCl}}_5(\mathrm{g})\rightleftharpoons {\mathrm{PCl}}_3(\mathrm{g})+{\mathrm{Cl}}_2(\mathrm{g})$ $5\text{ moles}$ of ${\mathrm{PCl}}_5$ are placed in a $200\text{ litre}$ vessel which contains $2\text{ moles}$ of ${\mathrm{N}}_2$ and is maintained at $600\text{ K}$. The equilibrium pressure is $2.46\text{ atm}$. The equilibrium constant ${\mathrm{K}}_{\mathrm{p}}$ for the dissociation of ${\mathrm{PCl}}_5$ is $\underline{}\times 10^{-3}$. (nearest integer) (Given : $\mathrm{R}=0.082{\text{ L atm K}}^{-1}{\text{ mol}}^{-1}$; Assume ideal gas behaviour)

Match List - I with List - II : $$\begin{array}{llll}& \text{List - I}& & \text{List - II}\\ & \text{(Colloid Preparation Method)}& & \text{(Chemical Reaction)}\\ \text{(a)}& \text{Hydrolysis}& \text{(i)}& 2\mathrm{AuC}{\mathrm{l}}_3+3\mathrm{HCHO}+3{\mathrm{H}}_2\mathrm{O}\to 2\mathrm{Au}(\mathrm{sol})+3\mathrm{HCOOH}+6\mathrm{HCl}\\ \text{(b)}& \text{Reduction}& \text{(ii)}& \mathrm{A}{\mathrm{s}}_2{\mathrm{O}}_3+3{\mathrm{H}}_2\mathrm{S}\to \mathrm{A}{\mathrm{s}}_2{\mathrm{S}}_3(\mathrm{sol})+3{\mathrm{H}}_2\mathrm{O}\\ \text{(c)}& \text{Oxidation}& \text{(iii)}& \mathrm{S}{\mathrm{O}}_2+2{\mathrm{H}}_2\mathrm{S}\to 3\mathrm{S}(\mathrm{sol})+2{\mathrm{H}}_2\mathrm{O}\\ \text{(d)}& \text{Double Decomposition}& \text{(iv)}& \mathrm{FeC}{\mathrm{l}}_3+3{\mathrm{H}}_2\mathrm{O}\to \mathrm{Fe}(\mathrm{OH}{)}_3(\mathrm{sol})+3\mathrm{HCl}\end{array}$$ Choose the most appropriate answer from the options given below.

1. A.(a)-(i), (b)-(iii), (c)-(ii), (d)-(iv)
2. B.(a)-(iv), (b)-(i), (c)-(iii), (d)-(ii)
3. C.(a)-(iv), (b)-(ii), (c)-(iii), (d)-(i)
4. D.(a)-(i), (b)-(ii), (c)-(iv), (d)-(iii)

The molar solubility of $\mathrm{Zn}(\mathrm{OH}{)}_2$ in $0.1\mathrm{M}\mathrm{NaOH}$ solution is $x\times 10^{-18}\mathrm{M}$. The value of x is ____. (Nearest integer) (Given : The solubility product of $\mathrm{Zn}(\mathrm{OH}{)}_2$ is $2\times 10^{-20}$)

The number of non-ionisable hydrogen atoms present in the final product obtained from the hydrolysis of $\mathrm{PC}{\mathrm{l}}_5$ is :

1. A.$0$
2. B.$2$
3. C.$1$
4. D.$3$

The equilibrium constant ${\mathrm{K}}_{\mathrm{c}}$ at 298 K for the reaction $\mathrm{A}+\mathrm{B}\rightleftharpoons \mathrm{C}+\mathrm{D}$ is 100. Starting with an equimolar solution with concentrations of A, B, C and D all equal to 1M, the equilibrium concentration of D is ___________ $\times 10^{-2}\text{ M}$. (Nearest integer)

The reaction rate for the reaction $[\mathrm{PtC}{\mathrm{l}}_4{]}^{2-}+{\mathrm{H}}_2\mathrm{O}\rightleftharpoons [\mathrm{Pt}({\mathrm{H}}_2\mathrm{O})\mathrm{C}{\mathrm{l}}_3{]}^{-}+{\mathrm{Cl}}^{-}$ was measured as a function of concentrations of different species. It was observed that $$\frac{-d\left[[\mathrm{PtC}{\mathrm{l}}_4{]}^{2-}\right]}{dt}=4.8\times 10^{-5}\left[[\mathrm{PtC}{\mathrm{l}}_4{]}^{2-}\right]-2.4\times 10^{-3}\left[[\mathrm{Pt}({\mathrm{H}}_2\mathrm{O})\mathrm{C}{\mathrm{l}}_3{]}^{-}\right][{\mathrm{Cl}}^{-}].$$ where square brackets are used to denote molar concentrations. The equilibrium constant ${\mathrm{K}}_{\mathrm{c}}=$ ___________. (Nearest integer)

A chloro compound "A". (i) forms aldehydes on ozonolysis followed by the hydrolysis. (ii) when vaporized completely 1.53 g of A, gives 448 mL of vapour at STP. The number of carbon atoms in a molecule of compound A is ___________.

The equilibrium constant for the reaction $\mathrm{A}(\mathrm{s})\rightleftharpoons \mathrm{M}(\mathrm{s})+\frac{1}{2}{\mathrm{O}}_2(\mathrm{g})$ is ${\mathrm{K}}_{\mathrm{p}}=4$. At equilibrium, the partial pressure of ${\mathrm{O}}_2$ is __________ atm. (Round off to the nearest integer)

10.0 mL of 0.05 M $\mathrm{KMn}{\mathrm{O}}_4$ solution was consumed in a titration with 10.0 mL of given oxalic acid dihydrate solution. The strength of given oxalic acid solution is __________ $\times 10^{-2}\text{ g/L}$. (Round off to the nearest integer)

For the reaction $\mathrm{A}+\mathrm{B}\rightleftharpoons 2C$ the value of equilibrium constant is 100 at 298 K. If the initial concentration of all the three species is 1 M each, then the equilibrium concentration of C is $x\times 10^{-1}$ M. The value of x is ____. (Nearest integer)

A reaction of benzonitrile with one equivalent $\mathrm{C}{\mathrm{H}}_3\mathrm{MgBr}$ followed by hydrolysis produces a yellow liquid "P". The compound "P" will give positive ____.

1. A.Iodoform test
2. B.Schiff's test
3. C.Ninhydrin's test
4. D.Tollen's test

An LPG cylinder contains gas at a pressure of 300 kPa at $27^{\circ }$. The cylinder can withstand the pressure of $1.2\times 10^6$ Pa. The room in which the cylinder is kept catches fire. The minimum temperature at which the bursting of cylinder will take place is ____ ${}^{\circ }$ C. (Nearest integer)

1. A.
2. B.
3. C.
4. D.