Mole Concept & Stoichiometry · JEE Main previous year questions

2019 12 questions

1. Q622019 · 12 Apr 2019 · Shift 1

   The mole fraction of a solvent in aqueous solution of a solute is 0.8. The molality (in ${\text{mol kg}}^{-1}$) of the aqueous solution is :

   1. A.$13.88\times 10^{-1}$
   2. B.$13.88\times 10^{-3}$
   3. C.$13.88$
   4. D.$13.88\times 10^{-2}$
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   Answer: C

2. Q782019 · 12 Apr 2019 · Shift 1

   5 moles of ${\text{AB}}_2$ weigh $125\times 10^{-3}\text{ kg}$ and 10 moles of ${\text{A}}_2{\text{B}}_2$ weigh $300\times 10^{-3}\text{ kg}$. The molar mass of A (${\text{M}}_{\text{A}}$) and molar mass of B (${\text{M}}_{\text{B}}$) in ${\text{kg mol}}^{-1}$ are:

   1. A.${\text{M}}_{\text{A}}=10\times 10^{-3}$ and ${\text{M}}_{\text{B}}=5\times 10^{-3}$
   2. B.${\text{M}}_{\text{A}}=25\times 10^{-3}$ and ${\text{M}}_{\text{B}}=50\times 10^{-3}$
   3. C.${\text{M}}_{\text{A}}=5\times 10^{-3}$ and ${\text{M}}_{\text{B}}=10\times 10^{-3}$
   4. D.${\text{M}}_{\text{A}}=50\times 10^{-3}$ and ${\text{M}}_{\text{B}}=25\times 10^{-3}$
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   Answer: C

3. Q752019 · 10 Apr 2019 · Shift 2

   The difference between $\Delta \mathrm{H}$ and $\Delta \mathrm{U}$ ($\Delta \mathrm{H}-\Delta \mathrm{U}$), when the combustion of one mole of heptane(l) is carried out at a temperature T, is equal to :

   1. A.- 4 RT
   2. B.3 RT
   3. C.- 3 RT
   4. D.4 RT
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   Answer: A

4. Q782019 · 9 Apr 2019 · Shift 2

   What would be the molality of 20% (mass/ mass) aqueous solution of KI? (molar mass of KI $=166\mathrm{g}\mathrm{mo}{\mathrm{l}}^{-1}$)

   1. A.1.51
   2. B.1.35
   3. C.1.08
   4. D.1.48
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   Answer: A

5. Q672019 · 8 Apr 2019 · Shift 2

   The percentage composition of carbon by mole in methane is :

   1. A.80%
   2. B.20%
   3. C.75%
   4. D.25%
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   Answer: B

6. Q752019 · 8 Apr 2019 · Shift 2

   5 moles of an ideal gas at 100 K are allowed to undergo reversible compression till its temperature becomes 200 K. If $C_V=28\mathrm{J}{\mathrm{K}}^{-1}\mathrm{mo}{\mathrm{l}}^{-1}$, calculate $\Delta U$ and $\Delta pV$ for this process. ($R=8.0\mathrm{J}{\mathrm{K}}^{-1}\mathrm{mo}{\mathrm{l}}^{-1}$)

   1. A.$\Delta U=14\mathrm{kJ}$; $\Delta (pV)=4\mathrm{kJ}$
   2. B.$\Delta U=2.8\mathrm{kJ}$; $\Delta (pV)=0.8\mathrm{kJ}$
   3. C.$\Delta U=14\mathrm{kJ}$; $\Delta (pV)=18\mathrm{kJ}$
   4. D.$\Delta U=14\mathrm{kJ}$; $\Delta (pV)=0.8\mathrm{kJ}$
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   Answer: A

7. Q882019 · 12 Jan 2019 · Shift 1

   Water samples with BOD values of 4 ppm and 18 ppm, respectively are :

   1. A.Clean and Highly polluted
   2. B.Highly polluted and Clean
   3. C.Highly polluted and Highly polluted
   4. D.Clean and Clean
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   Answer: A

8. Q892019 · 12 Jan 2019 · Shift 1

   The volume of gas A is twice than that of gas B. The compressibility factor of gas A is thrice than that of gas B at same temperature. The pressures of the gases for equal number of moles are -

   1. A.$2{\mathrm{P}}_{\mathrm{A}}=3{\mathrm{P}}_{\mathrm{B}}$
   2. B.$3{\mathrm{P}}_{\mathrm{A}}=2{\mathrm{P}}_{\mathrm{B}}$
   3. C.${\mathrm{P}}_{\mathrm{A}}=3{\mathrm{P}}_{\mathrm{B}}$
   4. D.${\mathrm{P}}_{\mathrm{A}}=2{\mathrm{P}}_{\mathrm{B}}$
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   Answer: A

9. Q722019 · 12 Jan 2019 · Shift 2

   8 g of NaOH is dissolved in 18g of ${\mathrm{H}}_2\mathrm{O}$. Mole fraction of NaOH in solution and molality (in $\mathrm{mol}\mathrm{k}{\mathrm{g}}^{-1}$) of the solution respectively are -

   1. A.0.2, 11.11
   2. B.0.167, 22.20
   3. C.0.167, 11.11
   4. D.0.2, 22.20
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   Answer: C

10. Q802019 · 9 Jan 2019 · Shift 1

    A solution of sodium sulphate contains $92\text{ g}$ of $\mathrm{N}{\mathrm{a}}^{+}$ ions per kilogram of water. The molality of $\mathrm{N}{\mathrm{a}}^{+}$ ions in that solution in ${\mathrm{mol}\mathrm{kg}}^{-1}$ is :

    1. A.12
    2. B.4
    3. C.8
    4. D.16
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    Answer: B

11. Q872019 · 9 Jan 2019 · Shift 1

    A water sample has ppm level concentration of the following metals : Fe = 0.2; Mn = 5.0; Cu = 3.0; Zn = 5.0. The metal that makes the water sample unsuitable for drinking is :

    1. A.Cu
    2. B.Mn
    3. C.Fe
    4. D.Zn
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    Answer: B

12. Q892019 · 9 Jan 2019 · Shift 1

    $0.5\text{ moles}$ of gas A and x moles of gas B exert a pressure of $200\text{ Pa}$ in a container of volume $10{\text{ m}}^3$ at $1000\text{ K}$. Given R is the gas constant in ${\mathrm{JK}}^{-1}{\mathrm{mol}}^{-1}$, x is :

    1. A.$\frac{2R}{4+R}$
    2. B.$\frac{2R}{4-R}$
    3. C.$\frac{4+R}{2R}$
    4. D.$\frac{4-R}{2R}$
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    Answer: D