Everything Science Grade 12

3.9 CHAPTER 3. REACTION RATES

3.9 Industrial applications ESCBG

The Haber process is a good example of anindustrial process whichuses the equilib-

rium principles that have been discussed. The equation for the process is as follows:

N 2 (g) + 3H 2 (g)� 2 NH 3 (g) + energy

Since the reaction is exothermic, the forward reaction isfavoured at low temperatures,

and the reverse reactionat high temperatures. Ifthe purpose of the Haber process is

to produce ammonia, then the temperature must be maintained at a level that is low

enough to ensure that the reaction continues in the forward direction.

The forward reaction isalso favoured by high pressures because there are fourmoles

of reactant for every twomoles of product formed.

The K value for this reaction will be calculated as follows:

Kc=

[NH 3 ]^2

[N 2 ][H 2 ]^3

Exercise 3 - 7

1. Look at the values of k calculated for the Haber process reaction at different
   temperatures, and thenanswer the questions that follow:

T(◦C) k

25 6.4 x 102

200 4.4 x 10 −^1

300 4.3 x 10 −^3

400 1.6 x 10 −^4

500 1.5 x 10 −^5

(a) What happens to thevalue of K as the temperature increases?

(b) Which reaction is being favoured when the temperature is 300 ◦C?

(c) According to this table, which temperature would be best if you wanted to

produce as much ammonia as possible? Explain.

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