Chemical & Ionic Equilibrium · JEE Main previous year questions

The minimum volume of water required to dissolve 0.1 g lead (II) chloride to get a saturated solution (${\text{K}}_{\text{sp}}$ of ${\text{PbCl}}_2=3.2\times 10^{-8}$, atomic mass of Pb = 207 u ) is :

1. A.0.36 L
2. B.17.98 L
3. C.0.18 L
4. D.1.798 L

Which of the following is a Lewis acid?

1. A.${\text{PH}}_3$
2. B.$\text{B}({\text{CH}}_3{)}_3$
3. C.NaH
4. D.${\text{NF}}_3$

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

Xenon hexafluoride on partial hydrolysis produces compounds 'X' and 'Y' . Compounds 'X' and 'Y' and the oxidation state of Xe are respectively :

1. A.${\text{XeO}}_2(+4)$ and ${\text{XeO}}_3(+6)$
2. B.${\text{XeOF}}_4(+6)$ and ${\text{XeO}}_3(+6)$
3. C.${\text{XeO}}_2{\text{F}}_2(+6)$ and ${\text{XeO}}_2(+4)$
4. D.${\text{XeOF}}_4(+6)$ and ${\text{XeO}}_2{\text{F}}_2(+6)$

Which of the following compounds contain(s) no covalent bond(s)? $\text{KCl},{\text{PH}}_3,{\text{O}}_2,{\text{B}}_2{\text{H}}_6,{\text{H}}_2{\text{SO}}_4$

1. A.$\text{KCl},{\text{B}}_2{\text{H}}_6$
2. B.$\text{KCl},{\text{B}}_2{\text{H}}_6,{\text{PH}}_3$
3. C.$\text{KCl},{\text{H}}_2{\text{SO}}_4$
4. D.$\text{KCl}$

An aqueous solution contains an unknown concentration of ${\text{Ba}}^{2+}$. When 50 mL of a 1 M solution of ${\text{Na}}_2{\text{SO}}_4$ is added, ${\text{BaSO}}_4$ just begins to precipitate. The final volume is 500 mL. The solubility product of ${\text{BaSO}}_4$ is $1\times 10^{-10}$. What is the original concentration of ${\text{Ba}}^{2+}$?

1. A.$1.0\times 10^{-10}\text{M}$
2. B.$5\times 10^{-9}\text{M}$
3. C.$2\times 10^{-9}\text{M}$
4. D.$1.1\times 10^{-9}\text{M}$

An aqueous solution contains $0.10\text{M}{\text{H}}_2\text{S}$ and $0.20\text{M}\text{HCl}$. If the equilibrium constants for the formation of ${\text{HS}}^{-}$ from ${\text{H}}_2\text{S}$ is $1.0\times 10^{-7}$ and that of ${\text{S}}^{2-}$ from ${\text{HS}}^{-}$ ions is $1.2\times 10^{-13}$ then the concentration of ${\text{S}}^{2-}$ ions in aqueous solution is :

1. A.$5\times 10^{-19}$
2. B.$5\times 10^{-8}$
3. C.$3\times 10^{-20}$
4. D.$6\times 10^{-21}$

Which of the following are Lewis acids?

1. A.${\text{BCl}}_3$ and ${\text{AlCl}}_3$
2. B.${\text{PH}}_3$ and ${\text{BCl}}_3$
3. C.${\text{AlCl}}_3$ and ${\text{SiCl}}_4$
4. D.${\text{PH}}_3$ and ${\text{SiCl}}_4$

An alkali is titrated against an acid with methyl orange as indicator, which of the following is a correct combination?

1. A.Base: Weak, Acid: Strong, End point: Colourless to pink
2. B.Base: Strong, Acid: Strong, End point: Pinkish red to yellow
3. C.Base: Weak, Acid: Strong, End point: Yellow to pinkish red
4. D.Base: Strong, Acid: Strong, End point: Pink to colourless

50 mL of 0.2 M ammonia solution is treated with 25 mL of 0.2 M HCl. If $\mathrm{p}{\mathrm{K}}_{\mathrm{b}}$ of ammonia solution is 4.75, the pH of the mixture will be :

1. A.$3.75$
2. B.$4.75$
3. C.$8.25$
4. D.$9.25$

1. A.(I) < (II) < (IV) < (III)
2. B.(I) < (II) < (III) < (IV)
3. C.(II) < (I) < (IV) < (III)
4. D.(II) < (I) < (III) < (IV)

$\mathrm{Xe}{\mathrm{F}}_6$ on partial hydrolysis with water produces a compound ‘X’. The same compound ‘X’ is formed when $\mathrm{Xe}{\mathrm{F}}_6$ reacts with silica. The compound ‘X’ is :

1. A.$\mathrm{Xe}{\mathrm{F}}_2$
2. B.$\mathrm{Xe}{\mathrm{F}}_4$
3. C.$\mathrm{XeO}{\mathrm{F}}_4$
4. D.$\mathrm{Xe}{\mathrm{O}}_3$

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

1. A.$4:5$
2. B.$1:10$
3. C.$10:1$
4. D.$5:4$

The equilibrium constant at $298\mathrm{K}$ for a reaction $\mathrm{A}+\mathrm{B}\rightleftharpoons \mathrm{C}+\mathrm{D}$ is $100$. If the initial concentration of all the four species were $1\mathrm{M}$ each, then equilibrium concentration of $\mathrm{D}$ (in $\mathrm{mol}{\mathrm{L}}^{-1}$) will be:

1. A.$0.818$
2. B.$1.818$
3. C.$1.182$
4. D.$0.182$

The following reaction is performed at $298\mathrm{K}$ $2\mathrm{NO}(\mathrm{g})+{\mathrm{O}}_2(\mathrm{g})\rightleftharpoons 2\mathrm{N}{\mathrm{O}}_2(\mathrm{g})$ The standard free energy of formation of $\mathrm{NO}(\mathrm{g})$ is $86.6kJ/mol$ at $298\mathrm{K}$. What is the standard free energy of formation of $\mathrm{N}{\mathrm{O}}_2(\mathrm{g})$ at $298\mathrm{K}$? (${\mathrm{K}}_{\mathrm{p}}=1.6\times 10^{12}$)

1. A.$86600+R(298)\ln (1.6\times 10^{12})$
2. B.$86600-\frac{\ln (1.6\times 10^{12})}{R(298)}$
3. C.$0.5[2\times 86,600-R(298)\ln (1.6\times 10^{12})]$
4. D.$R(298)\ln (1.6\times 10^{12})-86600$

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

For the reaction $\mathrm{S}{\mathrm{O}}_2(\mathrm{g})+\frac{1}{2}{\mathrm{O}}_2(\mathrm{g})\rightleftharpoons \mathrm{S}{\mathrm{O}}_3(\mathrm{g})$. if ${\mathrm{K}}_{\mathrm{p}}={\mathrm{K}}_{\mathrm{C}}(\mathrm{RT}{)}^{\mathrm{x}}$ where the symbols have usual meaning then the value of x is: (assuming ideality)

1. A.$-1$
2. B.$-1/2$
3. C.$1/2$
4. D.$1$

Among the following oxoacids, the correct decreasing order of acid strength is :

1. A.$\mathrm{HCl}{\mathrm{O}}_4>\mathrm{HCl}{\mathrm{O}}_3>\mathrm{HCl}{\mathrm{O}}_2>\mathrm{HOCl}$
2. B.$\mathrm{HCl}{\mathrm{O}}_2>\mathrm{HCl}{\mathrm{O}}_4>\mathrm{HCl}{\mathrm{O}}_3>\mathrm{HOCl}$
3. C.$\mathrm{HOCl}>\mathrm{HCl}{\mathrm{O}}_2>\mathrm{HCl}{\mathrm{O}}_3>\mathrm{HCl}{\mathrm{O}}_4$
4. D.$\mathrm{HCl}{\mathrm{O}}_4>\mathrm{HOCl}>\mathrm{HCl}{\mathrm{O}}_3>\mathrm{HCl}{\mathrm{O}}_2$

$8\mathrm{mol}$ of $\mathrm{A}{\mathrm{B}}_3(g)$ are introduced into a $1.0\mathrm{d}{\mathrm{m}}^3$ vessel. If it dissociates as $2A{\mathrm{B}}_3(g)\rightleftharpoons {\mathrm{A}}_2(g)+3{\mathrm{B}}_2(g)$. At equilibrium, $2\mathrm{mol}$ of ${\mathrm{A}}_2$ are found to be present. The equilibrium constant of this reaction is

1. A.2
2. B.3
3. C.27
4. D.36

Given (i) $\mathrm{HCN}(aq)+{\mathrm{H}}_2\mathrm{O}(l)\rightleftharpoons {\mathrm{H}}_3{\mathrm{O}}^{+}(aq)+\mathrm{C}{\mathrm{N}}^{-}(aq)K_a=6.2\times 10^{-10}$ (ii) $\mathrm{C}{\mathrm{N}}^{-}(aq)+{\mathrm{H}}_2\mathrm{O}(l)\rightleftharpoons \mathrm{HCN}(aq)+\mathrm{O}{\mathrm{H}}^{-}(aq)K_b=1.6\times 10^{-5}$. These equilibria show the following order of the relative base strength,

1. A.$\mathrm{O}{\mathrm{H}}^{-}>{\mathrm{H}}_2\mathrm{O}>\mathrm{C}{\mathrm{N}}^{-}$
2. B.$\mathrm{O}{\mathrm{H}}^{-}>\mathrm{C}{\mathrm{N}}^{-}>{\mathrm{H}}_2\mathrm{O}$
3. C.${\mathrm{H}}_2\mathrm{O}>\mathrm{C}{\mathrm{N}}^{-}>\mathrm{O}{\mathrm{H}}^{-}$
4. D.$\mathrm{C}{\mathrm{N}}^{-}>{\mathrm{H}}_2\mathrm{O}>\mathrm{O}{\mathrm{H}}^{-}$

A solution containing $0.85\mathrm{g}$ of $\mathrm{ZnC}{\mathrm{l}}_2$ in $125.0\mathrm{g}$ of water freezes at $-0.23^{\circ }\mathrm{C}$. The apparent degree of dissociation of the salt is ($K_f$ for $\mathrm{water}=1.86\mathrm{K}\mathrm{kg}\mathrm{mo}{\mathrm{l}}^{-1}$, atomic mass: $\mathrm{Zn}=65.3$ and $\mathrm{Cl}=35.5$)

1. A.$1.36\%$
2. B.$73.5\%$
3. C.$7.35\%$
4. D.$2.47\%$

The electron affinity of chlorine is 3.7 eV. 1 gram of chlorine is completely converted to $\mathrm{C}{\mathrm{l}}^{-}$ ion in a gaseous state. ($1\mathrm{eV}=23.06\mathrm{kcal}\mathrm{mo}{\mathrm{l}}^{-1}$). Energy released in the process is

1. A.4.8 kcal
2. B.7.2 kcal
3. C.8.2 kcal
4. D.2.4 kcal

The solubility (in $\mathrm{mol}{\mathrm{L}}^{-1}$) of AgCl ($K_{\mathrm{sp}}=1.0\times 10^{-10}$) in a 0.1 M KCl solution will be

1. A.$1.0\times 10^{-9}$
2. B.$1.0\times 10^{-10}$
3. C.$1.0\times 10^{-5}$
4. D.$1.0\times 10^{-11}$

$K_1,K_2$ and $K_3$ are the equilibrium constants of the following reactions (I), (II) and (III) respectively: (I) ${\mathrm{N}}_2+2{\mathrm{O}}_2\rightleftharpoons 2N{\mathrm{O}}_2$ (II) $2N{\mathrm{O}}_2\rightleftharpoons {\mathrm{N}}_2+2{\mathrm{O}}_2$ (III) $\mathrm{N}{\mathrm{O}}_2\rightleftharpoons \frac{1}{2}{\mathrm{N}}_2+{\mathrm{O}}_2$ The correct relation from the following is

1. A.$K_1=\frac{1}{K_2}=\frac{1}{K_3}$
2. B.$K_1=\frac{1}{K_2}=\frac{1}{(K_3{)}^2}$
3. C.$K_1=\sqrt{K_2}=K_3$
4. D.$K_1=\frac{1}{K_2}=K_3$

Solubility product of silver bromide is $5.0\times 10^{-13}$. The quantity of potassium bromide (molar mass taken as $120\mathrm{g}\mathrm{of}\mathrm{mo}{\mathrm{l}}^{-1}$) to be added to 1 litre of 0.05 M solution of silver nitrate to start the precipitation of AgBr is :

1. A.$1.2\times 10^{-10}\mathrm{g}$
2. B.$1.2\times 10^{-9}\mathrm{g}$
3. C.$6.2\times 10^{-5}\mathrm{g}$
4. D.$5.0\times 10^{-8}\mathrm{g}$