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JEE Advanced Chemistry Thermodynamics (C) 2020 JEE Advanced 2020 (Paper 2)

JEE Advanced Chemistry Question (2020) — Solution

Question

Tin is obtained from cassiterite by reduction with coke. Use the data given below to determine the minimum temperature (in K ) at which the reduction of cassiterite by coke would take place. 298   K :   Δ f H 0 SnO 2 ( s ) = - 581 . 0   kJ   mol - 1 ,   Δ f H 0 CO 2 ( g ) = - 394 . 0   kJ   mol - 1 S 0 SnO 2 ( s ) = 56 . 0   JK - 1   mol - 1 ,   S 0 ( Sn ( s ) ) = 52 . 0   JK - 1   mol - 1 S 0 ( C ( s ) ) = 6 . 0   JK - 1 mol - 1 ,   S 0 CO 2 ( g ) = 210 . 0   JK - 1 mol - 1 Assume that the enthalpies and the entropies are temperature independent.  

Options

  1. A. A
  2. B. B
  3. C. C
  4. D. D

Answer

A. A

Step-by-step solution

SnO 2 ( s ) + C ( s ) → Sn ( s ) + CO 2 ( g ) ΔH rxn 0 = ΔH f 0 CO 2 ( g ) - ΔH f 0 SnO 2 ( s ) = - 394 . 0 - [ - 581 . 0 ] = 187   KJ ΔS rxn 0 = S 0 ( Sn ( s ) ) + S 0 CO 2 ( g ) - S 0 SnO 2 , ( s ) - S 0 ( C ( s ) ) = 52 + 210 - 56 - 6 = 200   J ΔG ∘ = ΔH ∘ - TΔS ∘ For reaction to be spontaneous ΔG ∘ < 0 ΔH ∘ - TΔS ∘ < 0 187 × 1000 - T × 200 < 0 T > 935   K  

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