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AP EAMCET20228 Jul 2022Evening ShiftChemistryThermodynamics (C)Actual

The atomisation enthalpy of CH ₄ is 1660 ~kJ ~mol ⁻¹ . The C - H bond enthalpy of each successive step in CH ₄ CH ₃ CH ₂ CH are +15,+30 and +45 ~kJ ~mol ⁻¹ higher than the mean bond enthalpy of CH bonds, respectively. The bond enthalpy of the last C - H unit is

Options

  1. A400 ~kJ ~mol ⁻¹
  2. B325 ~kJ ~mol ⁻¹
  3. C475 ~kJ ~mol ⁻¹
  4. D385 ~kJ ~mol ⁻¹

Correct answer

B. 325 ~kJ ~mol ⁻¹

Step-by-step solution

The atomisation enthalpy of CH ₄ is 1660 ~kJ ~mol ⁻¹ . CH ₄(g) C (g)+4 H (g) ; _a H=1660 kJmol ⁻¹ CH ₄ 15 CH ₃ 30 CH ₂ 45 CH Mean C - H bond enthalpy = 1660 4 415=15+30+45+x x=415-90=325 ~kJ ~mol ⁻¹

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