Chemical & Ionic Equilibrium · JEE Main previous year questions

2012 6 questions

1. Q692012 · 12 May 2012 · Shift 1

   $8\mathrm{mol}$ 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
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   Answer: C

2. Q702012 · 12 May 2012 · Shift 1

   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.$\mathrm{C}{\mathrm{N}}^{-}>{\mathrm{H}}_2\mathrm{O}>\mathrm{O}{\mathrm{H}}^{-}$
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   Answer: B

3. Q742012 · 12 May 2012 · Shift 1

   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.$2.47\%$
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   Answer: B

4. Q662012 · 7 May 2012 · Shift 1

   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
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   Answer: D

5. Q672012 · 7 May 2012 · Shift 1

   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.$1.0\times 10^{-11}$
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   Answer: A

6. Q732012 · 7 May 2012 · Shift 1

   $K_1,K_2$ 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.$K_1=\frac{1}{K_2}=K_3$
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   Answer: B