The heat of formation of one mole of HI from hydrogen and iodine vapor at 27°C is -8000 cal. 2 1 H 2 ( g ) + 2 1 I 2 ( g ) → H I ( g ) ; Δ H = − 8000 c a l Calculate the heat of formation (in

Question

The heat of formation of one mole of HI from hydrogen and iodine vapor at 27°C is -8000 cal.

$\frac{1}{2} H_{2} (g) + \frac{1}{2} I_{2} (g) \to H I (g); Δ H = - 8000 c a l$

Calculate the heat of formation (in cal) at 127°C. Given:

$C_{p} = 7 + 6 \times 1 0^{- 3} T$ for hydrogen (g) (Cal/mol/K)

$C_{p} = 7 + 4 \times 1 0^{- 3} T$ for iodine (g) (Cal/mol/K)

$C_{p} = 7 + 3 \times 1 0^{- 3} T$ for HI (g) (Cal/mol/K)

TestHub · Accepted Answer

Given at 300 K: Δ H 300 ​ = − 8000 c a l Kirchhoff equation: Δ H 400 ​ = Δ H 300 ​ + ∫ 300 400 ​ Δ C p ​ d T Δ C p ​ = C p ​ ( H I ) − 2 1 ​ C p ​ ( H 2 ​ ) − 2 1 ​ C p ​ ( I 2 ​ ) = ( 7 + 0.003 T ) − 2 1 ​ ( 7 + 0.006 T ) − 2 1 ​ ( 7 + 0.004 T ) Δ C p ​ = − 0.002 T Δ H 400 ​ = − 8000 + ∫ 300 400 ​ ( − 0.002 T ) d T = − 8000 − 70 = − 8070 c a l

Chemistry - Thermochemistry Question with Solution | TestHub

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