JEE Chemistry - Chemical Energetics

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Question - 1

What is the heat of formation of HCI(g) from reaction \(\mathrm{H}_{2}(\mathrm{~g})+\mathrm{Cl}_{2}(\mathrm{~g}) \rightarrow 2 \mathrm{HCl}(\mathrm{g}) \cdot \Delta \mathrm{H}=44 \mathrm{kcal}\) .

  • A -3.2
  • B -22.00
  • C 1.23
  • D -9.0

Question - 2

When 10 gm of hydrogen gas at I atm pressure and 30oC ie brought to a reduced pressure \(\frac{1}{2} \) atm also at 3oC, calculate entropy change involved.

  • A 6.90
  • B 1.20
  • C 4.2
  • D 5.2

Question - 3

You are given Avogadro's number of "X" atoms. If half of the atoms of X transfer one electron to other half of 'X' atoms, 409 KJ must be added. If these X- ions are subsequently converted to X+, an addition 733 KI must be added. Calculate IP of X in eV. use \(\left(1 \mathrm{eV}=1.602 \times 10^{-19} \mathrm{~J} \text { and } \mathrm{N}_{\mathrm{A}}=6.023 \times 10^{23}\right)\)

  • A 12.30
  • B 4.21
  • C 11.84
  • D 23.0

Question - 4

The heat evolved on combustion of 1 gm starch \(\left(\mathrm{C}_{6} \mathrm{H}_{10} \mathrm{O}_{5}\right)_{\mathrm{n}} \text { into } \mathrm{CO}_{2} \text { and } \mathrm{H}_{2} \mathrm{O}(\ell) \text { is } 17.49 \mathrm{~kJ} \mathrm{gm}^{-1}\) Compute the enthalpy of formation of 1 gm starch . Given \(\Delta \mathrm{H}_{\mathrm{f}} \text { of } \mathrm{H}_{2} \mathrm{O}(\ell)=-285.85 \mathrm{~kJ} \mathrm{~mol}^{-1}, \Delta \mathrm{H}_{\mathrm{f}} \text { of }\) \(\mathrm{CO}_{2}=-293.7 \mathrm{~kJ} \text { mole }^{-1}\).

  • A -2.30
  • B 1.23
  • C -6.3
  • D -5.91

Question - 5

The heat of formation of \(\mathrm{CO}_{2}(\mathrm{~g}) \text { and } \mathrm{H}_{2} \mathrm{O}(l) \text { are }-94.3 \mathrm{kcal} \text { and }-68.4 \mathrm{kcal}\) respectively. Calculate heat of combustion of C6H6 if heat of formation of  C6H6 is + 11.72 kcal.

  • A -782.72
  • B 23.14
  • C -632.1
  • D 562.1

Question - 6

Calculate the heat of combustion of glucose from the following data 
\((i) \mathrm{C}_{\text {(graphite) }}+\mathrm{O}_{2} (g) \longrightarrow \mathrm{CO}_{2} (g), \Delta \mathrm{H}=-395.0 \mathrm{~kJ} \)
\((ii) \mathrm{H}_{2}(\mathrm{~g})+1 / 2 \mathrm{O}_{2} \longrightarrow \mathrm{H}_{2} \mathrm{O}(l), \Delta \mathrm{H}=-269.5 \mathrm{~kJ} \)
\((iii) 6 \mathrm{C}_{\text {(graphite) }}+6 \mathrm{H}_{2}(\mathrm{~g})+3 \mathrm{O}_{2}(\mathrm{~g}) \longrightarrow \mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}(\mathrm{~s}), \Delta \mathrm{H}=-1170 \mathrm{~kJ}\)

  • A -2817.00
  • B 12.300
  • C -63.01
  • D -963.2

Question - 7

Standard heat of combustion of \(\mathrm{C}_{2} \mathrm{H}_{2}(\mathrm{~g}) \text { and } \mathrm{C}_{2} \mathrm{H}_{4}(\mathrm{~g}) \text { are }-310.6 \mathrm{kcal} \text { and }-337.2 \mathrm{kcal}\) per mole respectively. Heat of formation of water is \(-68.3 \mathrm{kcal} \mathrm{mol}^{-1}\). Calculate heat of hydrogenation of \(\mathrm{C}_{2} \mathrm{H}_{2}(\mathrm{~g}) \text { to } \mathrm{C}_{2} \mathrm{H}_{4}(\mathrm{~g})\)

  • A 23.01
  • B -41.70
  • C 56.23
  • D -32.0

Question - 8

Calculate the heat evolved in the formation of 2.5 litre of CO at STP from its elements. Given that
\( \mathrm{C}+\mathrm{O}_{2} \longrightarrow \mathrm{CO}_{2} \Delta \mathrm{H}=-94.5 \mathrm{kcal} \)
\(2 \mathrm{CO}+\mathrm{O}_{2} \longrightarrow 2 \mathrm{CO}_{2} \Delta \mathrm{H}=-136.0 \mathrm{kcal} \)

  • A 6.23
  • B 1.23
  • C 2.96
  • D 3.21

Question - 9

The enthalpy for the following reactions \(\left(\Delta \mathrm{H}^{\circ}\right) \text { at } 25^{\circ} \mathrm{C}\) are given as :
\( 1 / 2 \mathrm{H}_{2}(\mathrm{~g})+1 / 2 \mathrm{O}_{2}(\mathrm{~g}) \longrightarrow \mathrm{OH}(\mathrm{g}): \Delta \mathrm{H}=10.06 \mathrm{kcals} \)
\(\mathrm{H}_{2}(\mathrm{~g}) \longrightarrow 2 \mathrm{H}(\mathrm{g}): \Delta \mathrm{H}=104.18 \mathrm{kcals} \)
\(\mathrm{O}_{2}(\mathrm{~g}) \longrightarrow 2 \mathrm{O}(\mathrm{g}): \Delta \mathrm{H}=118.32 \mathrm{kcals} \)
Calculate the O-H bond energy in the hydroxyl radical.

  • A -101.19
  • B 23.560
  • C -632.01
  • D 23.56

Question - 10

Calculate the enthalpy of the reaction.
\(\mathrm{CH}_{2}=\mathrm{CH}_{2}(\mathrm{~g})+\mathrm{H}_{2}(\mathrm{~g}) \longrightarrow \mathrm{CH}_{3}-\mathrm{CH}_{3}(\mathrm{~g})\)
Bond energies of \(\mathrm{C}-\mathrm{H}, \mathrm{C}-\mathrm{C}, \mathrm{C}=\mathrm{C} \text { and } \mathrm{H}-\mathrm{H} \text { are } 99,83,147 \text { and } 104 \mathrm{kcal}\) respectively.

  • A -308.70
  • B 23.015
  • C 23.015
  • D 1.25
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