Q22 / 87 · NTA Abhyas (JEE Main) 2020 · Chemistry · Chemical Equilibrium

For the reaction, 2 A g + B g ⇌ C g + D g ; K c = 1 0 1 2 . If the initial moles of A, B, C and D are 2,1,7 and 3 moles respectively in 1 L vessel, what is the equilibrium concentration of A?

  • Correct answer
    A
    4 × 1 0 - 4
  • B
    2 × 1 0 - 4
  • C
    10 - 4
  • D
    8 × 1 0 - 4

Solution

2 A g + B g ⇌ C g + D g Initial moles 2 1 7 3 At equilibrium 2 - 2 x 1 - x 7 + x 3 + x

∴   Due to very high value of K, we can assume that reactant almost gets converted into products, so

1 - x = y

2 - 2 x = 2 y ⇒ x ∼ 1

∴   1 0 1 2 = C D A 2 B

1 0 1 2 = 8 × 4 2 y 2 y

y 3 = 8 × 1 0 - 1 2

⇒   y = 2 × 1 0 - 4

∴   Equilibrium concentration of A = 2 y

= 2 × 2 × 1 0 - 4 = 4 × 1 0 - 4

Hence, the correct answer is option: 'A'.

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