Chemical & Ionic Equilibrium · JEE Main previous year questions

2020 18 questions

1. Q532020 · 6 Sept 2020 · Shift 1

   Arrange the following solutions in the decreasing order of pOH : (A) $0.01\text{ M }\mathrm{HCl}$ (B) $0.01\text{ M }\mathrm{NaOH}$ (C) $0.01\text{ M }\mathrm{C}{\mathrm{H}}_3\mathrm{COONa}$ (D) $0.01\text{ M }\mathrm{NaCl}$

   1. A.$\text{(B)}>\text{(C)}>\text{(D)}>\text{(A)}$
   2. B.$\text{(A)}>\text{(D)}>\text{(C)}>\text{(B)}$
   3. C.$\text{(A)}>\text{(C)}>\text{(D)}>\text{(B)}$
   4. D.$\text{(B)}>\text{(D)}>\text{(C)}>\text{(A)}$
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   Answer: B

2. Q542020 · 6 Sept 2020 · Shift 1

   For the reaction $$\mathrm{F}{\mathrm{e}}_2\mathrm{N}(\mathrm{s})+\frac{3}{2}{\mathrm{H}}_2(\mathrm{g})\rightleftharpoons 2\mathrm{Fe}(\mathrm{s})+\mathrm{N}{\mathrm{H}}_3(\mathrm{g})$$ the correct relation between $K_C$ and $K_p$ is :

   1. A.$K_C=K_p(RT{)}^{1/2}$
   2. B.$K_C=K_p(RT{)}^{-1/2}$
   3. C.$K_C=K_p(RT)$
   4. D.$K_C=K_p(RT{)}^{3/2}$
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   Answer: A

3. Q642020 · 6 Sept 2020 · Shift 1

   The variation of equilibrium constant with temperature is given below : | Temperature | Equilibrium Constant | | :--- | :--- | | $T_1=25^{\circ }\mathrm{C}$ | $K_1=10$ | | $T_2=100^{\circ }\mathrm{C}$ | $K_2=100$ | The values of $\Delta H^{\circ }$, $\Delta G^{\circ }$ at $T_1$ and $\Delta G^{\circ }$ at $T_2$ (in $\mathrm{kJ}\mathrm{mo}{\mathrm{l}}^{-1}$) respectively, are close to : $[\text{Use }R=8.314\mathrm{J}{\mathrm{K}}^{-1}\mathrm{mo}{\mathrm{l}}^{-1}]$

   1. A.$28.4$, $-5.71$ and $-14.29$
   2. B.$0.64$, $-7.14$ and $-5.71$
   3. C.$28.4$, $-7.14$ and $-5.71$
   4. D.$0.64$, $-5.71$ and $-14.29$
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   Answer: A

4. Q592020 · 6 Sept 2020 · Shift 2

   The value of $K_C$ is 64 at 800 K for the reaction $${\mathrm{N}}_2(\mathrm{g})+3{\mathrm{H}}_2(\mathrm{g})\rightleftharpoons 2N{\mathrm{H}}_3(\mathrm{g})$$ The value of $K_C$ for the following reaction is : $$\mathrm{N}{\mathrm{H}}_3(\mathrm{g})\rightleftharpoons \frac{1}{2}{\mathrm{N}}_2(\mathrm{g})+\frac{3}{2}{\mathrm{H}}_2(\mathrm{g})$$

   1. A.8
   2. B.$\frac{1}{8}$
   3. C.$\frac{1}{4}$
   4. D.$\frac{1}{64}$
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   Answer: B

5. Q722020 · 6 Sept 2020 · Shift 2· Numerical answer

   If the solubility product of $\mathrm{A}{\mathrm{B}}_2$ is $3.20\times 10^{-11}{\mathrm{M}}^3$, then the solubility of $\mathrm{A}{\mathrm{B}}_2$ in pure water is ______ $\times 10^{-4}\mathrm{mol}{\mathrm{L}}^{-1}$. [Assuming that neither kind of ion reacts with water]

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   Answer: 2

6. Q522020 · 3 Sept 2020 · Shift 1

   An acidic buffer is obtained on mixing :

   1. A.100 mL of 0.1 M HCl and 200 mL of $0.1\mathrm{M}\mathrm{C}{\mathrm{H}}_3\mathrm{COONa}$
   2. B.100 mL of 0.1 M HCl and 200 mL of 0.1 M NaCl
   3. C.100 mL of $0.1\mathrm{M}\mathrm{C}{\mathrm{H}}_3\mathrm{COOH}$ and 100 mL of 0.1 M NaOH
   4. D.100 mL of $0.1\mathrm{M}\mathrm{C}{\mathrm{H}}_3\mathrm{COOH}$ and 200 mL of 0.1 M NaOH
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   Answer: A

7. Q552020 · 3 Sept 2020 · Shift 2
   
   1. A.
   2. B.
   3. C.
   4. D.
   Show answer

   Answer: C

8. Q542020 · 2 Sept 2020 · Shift 1

   For the following Assertion and Reason, the correct option is Assertion (A): When $\mathrm{Cu}(\mathrm{II})$ and sulphide ions are mixed, they react together extremely quickly to give a solid. Reason (R): The equilibrium constant of $\mathrm{C}{\mathrm{u}}^{2+}(\mathrm{aq})+{\mathrm{S}}^{2-}(\mathrm{aq})\rightleftharpoons \mathrm{CuS}(\mathrm{s})$ is high because the solubility product is low.

   1. A.(A) is false and (R) is true.
   2. B.Both (A) and (R) are true but (R) is not the explanation for (A).
   3. C.Both (A) and (R) are true and (R) is the explanation for (A).
   4. D.Both (A) and (R) are false.
   Show answer

   Answer: B

9. Q742020 · 2 Sept 2020 · Shift 2· Numerical answer

   For the disproportionation reaction $2\mathrm{C}{\mathrm{u}}^{+}(\mathrm{aq})\rightleftharpoons \mathrm{Cu}(\mathrm{s})+\mathrm{C}{\mathrm{u}}^{2+}(\mathrm{aq})$ at 298 K. $\ln K$ (where K is the equilibrium constant) is _______ $\times 10^{-1}$. Given : $(E_{\mathrm{C}{\mathrm{u}}^{2+}/C{\mathrm{u}}^{+}}^{\circ }=0.16\mathrm{V}$ $E_{\mathrm{C}{\mathrm{u}}^{+}/Cu}^{\circ }=0.52\mathrm{V}$ $\frac{RT}{F}=0.025)$

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   Answer: 144

10. Q542020 · 9 Jan 2020 · Shift 1

    The ${\mathrm{K}}_{\mathrm{sp}}$ for the following dissociation is $1.6\times 10^{-5}$ $$\mathrm{PbC}{\mathrm{l}}_{2(\mathrm{s})}\leftrightharpoons \mathrm{P}{\mathrm{b}}_{(\mathrm{aq})}^{2+}+2C{\mathrm{l}}_{(\mathrm{aq})}^{-}$$ Which of the following choices is correct for a mixture of 300 mL 0.134 M $\mathrm{Pb}(\mathrm{N}{\mathrm{O}}_3{)}_2$ and 100 mL 0.4 M $\mathrm{NaCl}$ ?

    1. A.$\mathrm{Q}>{\mathrm{K}}_{\mathrm{sp}}$
    2. B.Not enough data provided
    3. C.$\mathrm{Q}<{\mathrm{K}}_{\mathrm{sp}}$
    4. D.$\mathrm{Q}={\mathrm{K}}_{\mathrm{sp}}$
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    Answer: A

11. Q702020 · 9 Jan 2020 · Shift 1
    
    1. A.$>1400{}^{\circ }\mathrm{C}$
    2. B.$>1200{}^{\circ }\mathrm{C}\text{ but }<1400{}^{\circ }\mathrm{C}$
    3. C.$<1400{}^{\circ }\mathrm{C}$
    4. D.$<1200{}^{\circ }\mathrm{C}$
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    Answer: A

12. Q562020 · 9 Jan 2020 · Shift 2
    
    1. A.1
    2. B.2
    3. C.8
    4. D.4
    Show answer

    Answer: B

13. Q582020 · 9 Jan 2020 · Shift 2

    The solubility product of $\mathrm{Cr}(\mathrm{OH}{)}_3$ at 298 K is $6.0\times 10^{-31}$. The concentration of hydroxide ions in a saturated solution of $\mathrm{Cr}(\mathrm{OH}{)}_3$ will be :

    1. A.$(2.22\times 10^{-31}{)}^{1/4}$
    2. B.$(4.86\times 10^{-29}{)}^{1/4}$
    3. C.$(18\times 10^{-31}{)}^{1/4}$
    4. D.$(18\times 10^{-31}{)}^{1/2}$
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    Answer: C

14. Q622020 · 8 Jan 2020 · Shift 1

    The strength of an aqueous $\mathrm{NaOH}$ solution is most accurately determined by titrating : (Note : consider that an appropriate indicator is used)

    1. A.Aq. $\mathrm{NaOH}$ in a pipette and aqueous oxalic acid in a burette
    2. B.Aq. $\mathrm{NaOH}$ in a burette and aqueous oxalic acid in a conical flask
    3. C.Aq. $\mathrm{NaOH}$ in a volumetric flask and concentrated ${\mathrm{H}}_2\mathrm{S}{\mathrm{O}}_4$ in a conical flask
    4. D.Aq. $\mathrm{NaOH}$ in a burette and concentrated ${\mathrm{H}}_2\mathrm{S}{\mathrm{O}}_4$ in a conical flask
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    Answer: B

15. Q712020 · 8 Jan 2020 · Shift 2· Numerical answer

    For an electrochemical cell $$\mathrm{Sn}(\mathrm{s})\mid \mathrm{S}{\mathrm{n}}^{2+}(\mathrm{aq},1M)\parallel \mathrm{P}{\mathrm{b}}^{2+}(\mathrm{aq},1M)\mid \mathrm{Pb}(\mathrm{s})$$ the ratio $\frac{[{\mathrm{Sn}}^{2+}]}{[{\mathrm{Pb}}^{2+}]}$ when this cell attains equilibrium is _______. (Given $E_{\mathrm{S}{\mathrm{n}}^{2+}|Sn}^0=-0.14\mathrm{V}$, $E_{\mathrm{P}{\mathrm{b}}^{2+}|Pb}^0=-0.13\mathrm{V}$, $\frac{2.303RT}{F}=0.06$)

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    Answer: 2.13 to 2.16

16. Q712020 · 7 Jan 2020 · Shift 1· Numerical answer

    Two solutions, A and B, each of 100L was made by dissolving 4g of $\mathrm{NaOH}$ and 9.8 g of ${\mathrm{H}}_2\mathrm{S}{\mathrm{O}}_4$ in water, respectively. The pH of the resultant solution obtained from mixing 40L of solution A and 10L of solution B is :

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    Answer: 10.6

17. Q722020 · 7 Jan 2020 · Shift 1· Numerical answer

    For the reaction : $$\mathrm{A}(l)\to 2\mathrm{B}(g)$$ $\Delta U=2.1\text{ kcal}$, $\Delta S=20\text{ cal }{K}^{-1}$ at $300\text{ K}$ Hence $\Delta G$ in kcal is :

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    Answer: -2.7

18. Q732020 · 7 Jan 2020 · Shift 2· Numerical answer

    3 g of acetic acid is added to 250 mL of 0.1 M HCl and the solution made up to 500 mL. To 20 mL of this solution $\frac{1}{2}\text{ mL}$ of 5 M NaOH is added. The pH of the solution is _______. [Given : pKa of acetic acid = 4.75, molar mass of acetic acid = 60 g/mol, $\log 3=0.4771$] Neglect any changes in volume.

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    Answer: 5.22 to 5.24