Chemical Thermodynamics · JEE Main previous year questions

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2021 10 questions

Q622021 · 27 Jul 2021 · Shift 2
The correct order of first ionisation enthalpy is :
1. A.Mg < S < Al < P
2. B.Mg < Al < S < P
3. C.Al < Mg < S < P
4. D.Mg < Al < P < S
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Answer: C
Q772021 · 25 Jul 2021 · Shift 1
At 298.2 K the relationship between enthalpy of bond dissociation (in $kJ mo l^{- 1}$ ) for hydrogen ( $E_{H}$ ) and its isotope, deuterium ( $E_{D}$ ), is best described by :
1. A. $E_{H} = \frac{1}{2} E_{D}$
2. B. $E_{H} = E_{D}$
3. C. $E_{H} ≃ E_{D} - 7.5$
4. D. $E_{H} = 2 E_{D}$
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Answer: C
Q872021 · 25 Jul 2021 · Shift 1· Numerical answer
At 298 K, the enthalpy of fusion of a solid (X) is $2.8 kJ mo l^{- 1}$ and the enthalpy of vaporisation of the liquid (X) is $98.2 kJ mo l^{- 1}$ . The enthalpy of sublimation of the substance (X) in $kJ mo l^{- 1}$ is ____. (in nearest integer)
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Answer: 101
Q862021 · 22 Jul 2021 · Shift 2· Numerical answer
If the standard molar enthalpy change for combustion of graphite powder is $- 2.48 \times 1 0^{2} kJ mo l^{- 1}$ , the amount of heat generated on combustion of 1 g of graphite powder is ____ kJ. (Nearest integer)
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Answer: 21
Q842021 · 18 Mar 2021 · Shift 1· Numerical answer
For the reaction $C_{2} H_{6} \to C_{2} H_{4} + H_{2}$ the reaction enthalpy $Δ_{r} H =$ ____ $kJ mo l^{- 1}$ . (Round off to the Nearest Integer). [ Given : Bond enthalpies in $kJ mo l^{- 1} : C - C : 347, C = C : 611; C - H : 414, H - H : 436]$
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Answer: 128
Q892021 · 18 Mar 2021 · Shift 1· Numerical answer
For the reaction $2 F e^{3 +} (aq) + 2 I^{-} (aq) \to 2 F e^{2 +} (aq) + I_{2} (s)$ the magnitude of the standard molar Gibbs free energy change, $Δ_{r} G_{m}^{o} = -$ ____ kJ (Round off to the Nearest Integer). $[E_{F e^{2 +} /Fe (s)}^{o} = - 0.440 V; E_{I_{2} /2 I^{-}}^{o} = 0.539 V; E_{F e^{3 +} /Fe (s)}^{o} = - 0.036 V F = 96500 C]$
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Answer: 46
Q812021 · 26 Feb 2021 · Shift 1· Numerical answer
For a chemical reaction $A + B ⇌ C + D$ $(Δ_{r} H^{⊖} = 80 kJ mo l^{- 1})$ the entropy change $Δ_{r} S^{⊖}$ depends on the temperature T (in K) as $Δ_{r} S^{⊖} = 2 T (J K^{- 1} mo l^{- 1})$ . Minimum temperature at which it will become spontaneous is _________ K. (Integer)
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Answer: 200
Q742021 · 26 Feb 2021 · Shift 2
The correct order of electron gain enthalpy is :
1. A.Te > Se > S > O
2. B.S > Se > Te > O
3. C.S > O > Se > Te
4. D.O > S > Se > Te
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Answer: B
Q842021 · 26 Feb 2021 · Shift 2· Numerical answer
The average S-F bond energy in $kJ mo l^{- 1}$ of $S F_{6}$ is _________. (Rounded off to the nearest integer) [Given : The values of standard enthalpy of formation of $S F_{6} (g)$ , S(g) and F(g) are - 1100, 275 and 80 $kJ mo l^{- 1}$ respectively.]
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Answer: 309
Q742021 · 25 Feb 2021 · Shift 2
The correct order of bond dissociation enthalpy of halogens is :
1. A. $F_{2} > C l_{2} > B r_{2} > I_{2}$
2. B. $C l_{2} > B r_{2} > F_{2} > I_{2}$
3. C. $I_{2} > B r_{2} > C l_{2} > F_{2}$
4. D. $C l_{2} > F_{2} > B r_{2} > I_{2}$
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Answer: B