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← IIT-JEE 2011 · Paper 2
ChemistryMatrix match+8Question 19 of 60

IIT-JEE 2011 · Paper 2, Chemistry question 19

Match the transformations in column I with appropriate options in column II

Column I

  • A
    COX2(s)→COX2(g)\ce{CO2(s) -> CO2(g)}
  • B
    CaCOX3(s)→CaO(s)+COX2(g)\ce{CaCO3(s) -> CaO(s) + CO2(g)}
  • C
    2 HX ∙ →HX2(g)\ce{2H^. -> H2(g)}
  • D
    PX(white, solid)→PX (red,solid)\ce{P_{(white, solid)} -> P_{(red, solid)}}

Column II

  • P
    phase transition
  • Q
    allotropic change
  • R
    ΔH\Delta H is positive
  • S
    ΔS\Delta S is positive
  • T
    ΔS\Delta S is negative
Mark every match for each entry
PQRST
A
B
C
D
Answer and worked solution

Official answer: A → P, R, S; B → R, S; C → T; D → P, Q, T

  • A (sublimation): a phase transition, endothermic, gas formed. → P, R, S.
  • B (decomposition of CaCOX3\ce{CaCO3}): endothermic, gas formed. → R, S.
  • C (bond formation): exothermic, two particles become one. → T.
  • D (white → red phosphorus): an allotropic change, also counted as a solid-solid phase transition. Red phosphorus is polymeric and more ordered, so entropy falls (and the change is exothermic). → P, Q, T.

Answer: A → P, R, S; B → R, S; C → T; D → P, Q, T

Topics:EntropyFirst law and enthalpy
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