Q12 / 160 · TS EAMCET 2021 (05 Aug Shift 1) · Chemistry

The equilibrium constant Kp for the formation of ammonia from its constituent elements at 27°C is 1.2×10-4 and at 127°C is 0.60×10-4. Calculate the mean heat of formation of ammonia per mole in this temperature range.

  • A
    -82.64Cal
  • B
    -826.4Cal
  • Correct answer
    C
    -1652.8Cal
  • D
    -165.2Cal

Solution

logK2K1 = ∆H2.303R1T1-1T2

Where K2 is equilibrium constant at higher temperature = 0.60 ×10-4K1 is equilibrium constant at lower temperature = 1.2 ×10-4T2 = 127°C = 400KT1 = 27 °C = 300 K∆H = Heat of formation of ammonia per mole = ?

log0.61.2 = ∆H2.303×1.98 cal1300-1400∆H = 2.303×1.98×1200×(-0.30)1 = -1652.8 cal

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

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