Quantrex Quantrex AcademyJEE · NEET · NDA PYQs with solutions Open app
Most Important Selected Qs for JEE AdvancedChemistryThermodynamics (C)

Paragraph: Consider the following data (all values in kJ mol ⁻¹ at 25^ C ) and answer the questions that follow. (i) Enthalpy of polymerisation of ethene =-72 (ii) Enthalpy of formation of benzene (I) =49 (iii) Enthalpy of vaporisation of benzene ( I )=30 (iv) Resonance energy of benzene =-152 (v) Heat of formation of gaseous atoms from the element in their standard state: H =218, C =715 and average C - H bond energy

Options

  1. A267.05 ~kJ ~mol ⁻¹
  2. B201.67 ~kJ ~mol ⁻¹
  3. C271.66 kJ mol-1
  4. D323.50 ~kJ ~mol ⁻¹

Correct answer

C. 271.66 kJ mol-1

Step-by-step solution

Let B.E. of C=C be x and B . E . of C-C be y n ( CH ₂= CH ₂ ) ( CH ₂- CH ₂⁻ )_ n x-2 y=-72 ...(i) aligned & H_r= H_f (C₆ H₆, I )+ H_ vap (C₆ H₆, I )-R E & =49+30-(-152)=231 & 231=6 715+6 218-3(x+y)-6 415 aligned x+y=959 On solving (i) and (ii) we get x=615.33 and y=343.67

Practice Thermodynamics (C) on Quantrex Academy →

More from Thermodynamics (C)

An ideal gas ( 0.5 mol), initially at 2 bar pressure, is compressed at a constant temperature of 600 K in two steps: first, against a constant external pressure of P bar ( 2 < P < 2026List-I contains various physical/chemical processes, and List-II contains combinations of changes in enthalpy ( H ) and entropy ( S ). Match each entry in List-I to the appropriate 2026Consider the reaction 2 H ₂ S (g) + 3 O ₂(g) 2 H ₂ O (l) + 2 SO ₂(g) The magnitude of enthalpy change for the reaction in kJ mol ⁻¹ is ________. (Nearest integer) Given: _fH^ ( H ₂ 2026Match List - I with List - II. Given V₁ and V₂ are initial and final volumes respectively. List - I (Isothermal process) List - II (Expression) A. Reversible expansion I. q = 0 B. 2026Arrange the following isothermal processes in order of the magnitude of the work ( p - V ) involved between states 1 and 2 . A. Expansion in single stage w_A B. Expansion in multi 2026Consider the reaction X Y at 300 K. If H^ and K are 28.40 kJ mol ⁻¹ and 1.8 10⁻⁷ at the same temperature, then the magnitude of S^ for the reaction in J K ⁻¹ mol ⁻¹ is _______. (Ne 2026Consider the following data for the reaction X₂(g) + Y₂(g) 2XY(g) at 600 K . The _r G^ (in kJ mol ⁻¹ ) for the reaction is : Compound _f H^ _ 600K (kJ mol ⁻¹ ) S^ _ 600K (J mol ⁻¹ 2026The correct order of molar heat capacities measured at 298 K and 1 bar is : 2026 Full Thermodynamics (C) list All Most Important Selected Qs for JEE Advanced PYQs