Chemical Thermodynamics · JEE Main previous year questions

2019 6 questions

1. Q672019 · 12 Apr 2019 · Shift 1

   Enthalpy of sublimation of iodine is $24{\text{ cal g}}^{-1}$ at $200{}^{\circ }\text{C}$. If specific heat of ${\text{I}}_2\text{(s)}$ and ${\text{I}}_2\text{ (vap)}$ are 0.055 and $0.031{\text{ cal g}}^{-1}{\text{K}}^{-1}$ respectively, then enthalpy of sublimation of iodine at $250{}^{\circ }\text{C}$ in ${\text{cal g}}^{-1}$ is :

   1. A.2.85
   2. B.22.8
   3. C.11.4
   4. D.5.7
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   Answer: B

2. Q712019 · 10 Apr 2019 · Shift 1

   A process will be spontaneous at all temperatures if :

   1. A.$\Delta \mathrm{H}<0$ and $\Delta \mathrm{S}>0$
   2. B.$\Delta \mathrm{H}<0$ and $\Delta \mathrm{S}<0$
   3. C.$\Delta \mathrm{H}>0$ and $\Delta \mathrm{S}<0$
   4. D.$\Delta \mathrm{H}>0$ and $\Delta \mathrm{S}>0$
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   Answer: A

3. Q692019 · 9 Apr 2019 · Shift 2
   
   1. A.Formation of A and B from C has highest enthalpy of activation.
   2. B.D is kinetically stable product.
   3. C.C is the thermodynamically stable product
   4. D.Activation enthalpy to form C is $5\mathrm{kJ}\mathrm{mo}{\mathrm{l}}^{-1}$ less than that to form D.
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   Answer: D

4. Q702019 · 12 Jan 2019 · Shift 2

   Given (i) $\mathrm{C}(\mathrm{graphite})+{\mathrm{O}}_2(\mathrm{g})\to \mathrm{C}{\mathrm{O}}_2(\mathrm{g})$; ${\Delta }_r{H}^{\ominus }=x\mathrm{kJ}\mathrm{mo}{\mathrm{l}}^{-1}$ (ii) $\mathrm{C}(\mathrm{graphite})+\frac{1}{2}{\mathrm{O}}_2(\mathrm{g})\to \mathrm{CO}(\mathrm{g})$; ${\Delta }_r{H}^{\ominus }=y\mathrm{kJ}\mathrm{mo}{\mathrm{l}}^{-1}$ (iii) $\mathrm{CO}(\mathrm{g})+\frac{1}{2}{\mathrm{O}}_2(\mathrm{g})\to \mathrm{C}{\mathrm{O}}_2(\mathrm{g})$; ${\Delta }_r{H}^{\ominus }=z\mathrm{kJ}\mathrm{mo}{\mathrm{l}}^{-1}$ Based on the above thermochemical equations, find out which one of the following algebraic relationships is correct?

   1. A.z = x + y
   2. B.x = y + z
   3. C.x = y − z
   4. D.y = 2z − x
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   Answer: B

5. Q692019 · 11 Jan 2019 · Shift 2

   The standard reaction Gibbs energy for a chemical reaction at an absolute temperature T is given by $${\Delta }_{\mathrm{r}}{\mathrm{G}}^{\circ }=\mathrm{A}-\mathrm{BT}$$ Where A and B are non-zero constants. Which of the following is TRUE about this reaction?

   1. A.Exothermic if $\mathrm{B}<0$
   2. B.Endothermic if $\mathrm{A}>0$
   3. C.Exothermic if $\mathrm{A}>0$ and $\mathrm{B}<0$
   4. D.Endothermic if $\mathrm{A}<0$ and $\mathrm{B}>0$
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   Answer: B

6. Q822019 · 9 Jan 2019 · Shift 1
   
   1. A.
   2. B.
   3. C.
   4. D.
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   Answer: C