Passage IV

Ammonia (NH3) can be produced according to the chemical equation

N2 + 3H22NH3

The equilibrium arrow () indicates that this reaction proceeds in both directions until it is at equilibrium, so that both the forward reaction (production of NH3 ) and the backward reaction (production of N2 and H2 ) occur at the same rate. Equilibrium can be shifted forward or backward by changing the temperature, pressure, or concentration of reactants or products.

Two experiments were done using the following apparatus to produce NH3.

In each trial, Steps 1−4 occurred:

1. A fresh catalyst (Catalyst W, X, Y, or Z), 160 kg of H2, and 745 kg of N2 were placed in the reactor.

2. The H2 and N2 reacted at a constant temperature and a constant pressure until equilibrium was established.

3. A mixture of NH3 and any unreacted H2 and N2 flowed through Pipe A to a −50°C condenser at 1 atmosphere (atm) of pressure.

4. NH3 condensed and exited the apparatus. (H2 and N2 do not condense at −50°C.) Any unreacted H2 and N2 flowed into Pipe B, returning to the reactor.

Steps 2−4 reoccurred in cycles until no more H2 and N2 returned from the condenser.

Experiment 1

A set of 9 trials was conducted with each of the 4 catalysts. For each set, the pressure was 150 atm; within each set, the temperature was different for each trial. Figure 1 shows, for each trial, the number of cycles of Steps 2−4.

Experiment 2

Four sets of 9 trials each were conducted with Catalyst Z. For each set, the temperature was different; within each set, the pressure was different for each trial. Figure 2 shows, for each trial, the amount of NH3 produced in the first cycle of Steps 2−4.

Diagram and figures adapted from Jayant M. Modak, "Haber Process for Ammonia Synthesis." ©2002 by Indian Academy of Sciences.

23. The movement of H2 and N2 through the apparatus as Steps 1−4 occurred is best represented by which of the following expressions?

Answer and Explanation

Your Answer is

Correct Answer is C

Explanation

Look at the experimental steps, the first step is to put it in the reactor, the third step is to reach the condenser through Pipe A, and the fourth step is to enter Pipe B.