Chemical & Ionic Equilibrium · JEE Main previous year questions

2010 4 questions

1. Q682010 · 25 Apr 2010 · Shift 1

   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.$5.0\times 10^{-8}\mathrm{g}$
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   Answer: B

2. Q692010 · 25 Apr 2010 · Shift 1

   At $25^{\circ }\mathrm{C}$, the solubility product of $\mathrm{Mg}(\mathrm{OH}{)}_2$ is $1.0\times 10^{-11}$. At which pH, will $\mathrm{M}{\mathrm{g}}^{2+}$ ions start precipitating in the form of $\mathrm{Mg}(\mathrm{OH}{)}_2$ from a solution of 0.001 M $\mathrm{M}{\mathrm{g}}^{2+}$ ions?

   1. A.9
   2. B.10
   3. C.11
   4. D.8
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   Answer: B

3. Q702010 · 25 Apr 2010 · Shift 1

   The correct order of increasing basicity of the given conjugate bases ($\mathrm{R}=\mathrm{C}{\mathrm{H}}_3$) is

   1. A.$R\mathrm{CO}\overline{\mathrm{O}}<HC\equiv \overline{C}<\overline{R}<\overline{\mathrm{N}}{\mathrm{H}}_2$
   2. B.$\overline{R}<HC\equiv \overline{C}<R\mathrm{CO}\overline{\mathrm{O}}<\overline{\mathrm{N}}{\mathrm{H}}_2$
   3. C.$R\mathrm{CO}\overline{\mathrm{O}}<\overline{\mathrm{N}}{\mathrm{H}}_2<HC\equiv \overline{C}<\overline{R}$
   4. D.$R\mathrm{CO}\overline{\mathrm{O}}<HC\equiv \overline{C}<\overline{\mathrm{N}}{\mathrm{H}}_2<\overline{R}$
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   Answer: D

4. Q782010 · 25 Apr 2010 · Shift 1

   Consider the reaction : $\mathrm{C}{\mathrm{l}}_2(\mathrm{aq})+{\mathrm{H}}_2\mathrm{S}(\mathrm{aq})\to \mathrm{S}(\mathrm{s})+2{\mathrm{H}}^{+}(\mathrm{aq})+2C{\mathrm{l}}^{-}(\mathrm{aq})$ The rate equation for this reaction is rate = $\mathrm{k}[\mathrm{C}{\mathrm{l}}_2][{\mathrm{H}}_2\mathrm{S}]$ Which of these mechanisms is/are consistent with this rate equation? (A) $\mathrm{C}{\mathrm{l}}_2+{\mathrm{H}}_2\mathrm{S}\to {\mathrm{H}}^{+}+\mathrm{C}{\mathrm{l}}^{-}+\mathrm{C}{\mathrm{l}}^{+}+\mathrm{H}{\mathrm{S}}^{-}$ (slow) $\mathrm{C}{\mathrm{l}}^{+}+\mathrm{H}{\mathrm{S}}^{-}\to {\mathrm{H}}^{+}+\mathrm{C}{\mathrm{l}}^{-}+\mathrm{S}$ (fast) (B) ${\mathrm{H}}_2\mathrm{S}\iff {\mathrm{H}}^{+}+\mathrm{H}{\mathrm{S}}^{-}$ (fast equilibrium) $\mathrm{C}{\mathrm{l}}_2+\mathrm{H}{\mathrm{S}}^{-}\to 2C{\mathrm{l}}^{-}+{\mathrm{H}}^{+}+\mathrm{S}$ (slow)

   1. A.B only
   2. B.Both A and B
   3. C.Neither A nor B
   4. D.A only
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   Answer: D