Ammonia equilibrium: measured and computed

Equilibrium ammonia percentages measured over an iron catalyst for a 3 : 1 hydrogen–nitrogen feed in 1923–1924, beside the values this site computes from NIST thermodynamic data for ideal gases.


325	10	10.38	11.13	−0.75
350	10	7.35	7.89	−0.54
375	10	5.25	5.63	−0.38
400	10	3.85	4.06	−0.21
425	10	2.80	2.97	−0.17
450	10	2.04	2.20	−0.16
475	10	1.61	1.66	−0.05
500	10	1.20	1.27	−0.07
350	30	17.80	18.52	−0.72
375	30	13.35	14.02	−0.67
400	30	10.09	10.58	−0.49
425	30	7.59	8.01	−0.42
450	30	5.80	6.10	−0.30
475	30	4.53	4.68	−0.15
500	30	3.48	3.63	−0.15
350	50	25.11	25.68	−0.57
375	50	19.44	20.15	−0.71
400	50	15.11	15.68	−0.57
425	50	11.71	12.17	−0.46
450	50	9.17	9.45	−0.28
500	50	5.58	5.78	−0.20
375	100	30.95	30.52	0.43
400	100	24.91	24.89	0.02
425	100	20.23	20.13	0.10
450	100	16.35	16.19	0.16
475	100	12.98	12.99	−0.01
500	100	10.40	10.44	−0.04
450	300	35.50	31.98	3.52
475	300	31.00	27.25	3.75
500	300	26.20	23.09	3.11
450	600	53.60	43.75	9.85
475	600	47.50	38.70	8.80
500	600	42.10	34.00	8.10
450	1000	69.40	52.34	17.06
475	1000	63.50	47.43	16.07

Below 100 atm the two agree to within one percentage point; at higher pressures the measured yields are larger because ammonia is far from ideal (fugacity coefficients below 1).

Sources

A. T. Larson, R. L. Dodge, “The ammonia equilibrium”, J. Am. Chem. Soc. 45, 2918–2930 (1923).
A. T. Larson, “The ammonia equilibrium at high pressures”, J. Am. Chem. Soc. 46, 367–372 (1924).
Computed values: NIST Chemistry WebBook Shomate parameters, ideal gases.

Used in these lessons

The Haber process: an industrial compromise