Use a copy of the Periodic Table where you need one.
Ammonia is produced by the Haber process. Which statement about the process is not correct?
Source: Zhonghua Prelim P1 Q32 (adapted)
Which condition(s) used in the Haber process can increase both the reaction rate and the yield?
1 operating at a high pressure
2 operating at a high temperature
3 using a finely divided catalyst
Source: 2024 Jurongville Prelim P1 Q23
Suppose unreacted gases are not recycled. What volumes of nitrogen and hydrogen are needed to produce 600 dm3 of ammonia in a process that is only 15% efficient?
| volume of N2 / dm3 | volume of H2 / dm3 | |
|---|---|---|
| A | 45 | 135 |
| B | 255 | 765 |
| C | 300 | 900 |
| D | 2000 | 6000 |
Source: 2024 Jurongville Prelim P1 Q16
The forward reaction of the Haber process is N2(g) + 3H2(g) → 2NH3(g). 15 cm3 of nitrogen is added to 60 cm3 of hydrogen in a container. What is the total volume of gas remaining in the container after the reaction is complete?
Source: 2023 GESS Sec 3 End-of-Year P1 Q25
Ammonium chloride is heated strongly in a boiling tube. Damp blue and red litmus papers are placed at the mouth of the boiling tube. Which row shows the correct sequence of observations that would be made?
| first observed colour change | final colour of both litmus papers | |
|---|---|---|
| A | The damp blue litmus paper turns red. | red |
| B | The damp blue litmus paper turns red then bleaches. | white |
| C | The damp red litmus paper turns blue. | blue |
| D | The damp red litmus paper turns blue. | red |
Source: 2024 CGS Prelim P1 Q16
Ammonia is manufactured by the Haber process: N2(g) + 3H2(g) ⇌ 2NH3(g). The economics of the process require that as much ammonia as possible is made as quickly as possible. The table shows how the percentage of ammonia varies with the conditions.
| pressure / atm | 100 | 200 | 300 | 400 |
|---|---|---|---|---|
| % ammonia at 300 °C | 45 | 65 | 72 | 78 |
| % ammonia at 500 °C | 9 | 18 | 25 | 31 |
Source: 2024 GESS Prelim P2 Q6
In the Haber process, N2(g) + 3H2(g) ⇌ 2NH3(g). A chemical engineering company evaluated different operating conditions for a new ammonia plant. Table 1 shows the yield of ammonia at 200 atm and different temperatures. Table 2 shows the yield at 450 °C and different pressures, with the estimated annual cost of running the plant.
| temperature / °C | yield of NH3 / % |
|---|---|
| 350 | 38.5 |
| 400 | 31.4 |
| 450 | 24.8 |
| 500 | 18.9 |
| 550 | 14.1 |
| pressure / atm | yield of NH3 / % | annual cost / million dollars |
|---|---|---|
| 100 | 14.5 | 105 |
| 150 | 20.3 | 118 |
| 200 | 24.8 | 135 |
| 250 | 27.9 | 167 |
| 300 | 30.1 | 215 |
Source: 2026 PLMGS Prelim P2 Q7 (adapted)
Ammonia is manufactured industrially in the Haber process.
Source: 2025 Christ Church Prelim P2 Q5
DThe process involves a non-reversible reaction.[1]
The Haber process is reversible: ammonia breaks down into nitrogen and hydrogen as it forms.
C1 only[1]
A high pressure increases both. A high temperature speeds up the reaction but lowers the yield, and a catalyst speeds up the reaction without changing the yield.
D2000 dm3 of nitrogen and 6000 dm3 of hydrogen[1]
Volume of ammonia if the reaction were complete = 600 × 10015 = 4000 dm3.
N2 : H2 : NH3 = 1 : 3 : 2, so 2000 dm3 of nitrogen and 6000 dm3 of hydrogen are needed.
C45 cm3[1]
15 cm3 of nitrogen reacts with 45 cm3 of hydrogen to form 30 cm3 of ammonia. 15 cm3 of hydrogen is left over, so the total is 30 + 15 = 45 cm3.
DThe damp red litmus paper turns blue first, and both papers end red.[1]
Ammonia (Mr 17) diffuses faster than hydrogen chloride (Mr 36.5), so it reaches the papers first and turns the red paper blue. Hydrogen chloride arrives later and turns both papers red.
By the cracking of crude oil fractions (hydrocarbons). [1]
Nitrogen has the electronic structure 2.5, with 5 valence electrons. [1]
It needs three more electrons to fill its valence shell, so it shares one electron with each of three hydrogen atoms. [1]
As the temperature increases, the yield decreases. [1]
It increases the yield of ammonia. [1]
A higher pressure is a safety risk (risk of explosion) or the plant is too expensive to build to withstand it. [1]
They are recycled: sent over the catalyst again. [1]
The yield of ammonia decreases (from 38.5% to 14.1%) as the temperature increases (from 350 °C to 550 °C). [1]
From 100 to 300 atm the yield increases by 30.1 − 14.5 = 15.6%, and from 550 °C to 350 °C it increases by 38.5 − 14.1 = 24.4%. [1]
This is 0.078% for every 1 atm and 0.122% for every 1 °C. [1]
No, I do not agree: decreasing the temperature produces a larger increase in the yield. [1]
It contributes to greenhouse gas emissions, leading to global warming. [1]
N2(g) + 3H2(g) ⇌ 2NH3(g) [1]
From the equation, 1 volume of nitrogen reacts with 3 volumes of hydrogen. [1]
About 450 °C, about 250 atm and a finely divided iron catalyst (all three for the mark). [1]
Upward delivery [1]
because ammonia is less dense than air. [1]
NH3 : NO = 1 : 1 by volume, so the theoretical volume of NO = 440 dm3 [1]
Volume collected = 40100 × 440 = 176 dm3 [1]