Chapter 10 - Haber Process (10.3)

Question 1

Where is nitrogen obtained from (Haber process)

and explanation

Answer 1

From the air
Since air is nearly 80% nitrogen and roughly 20% oxygen, the oxygen is removed by burning hydrogen (combustion). This leaves mainly nitrogen and small amounts of other gasses.

Question 2

Where is hydrogen obtained from (Haber process)

Answer 2

1) Reacting natural gas (methane) with steam

2) Cracking hydrocarbons

Question 3

Chemical reactions for obtaining hydrogen

Answer 3

1) Reacting natural gas (methane) with steam

……………………………(catalyst)
CH4 (g) + 2H2O (g) —-> CO2 (g) + 4H2 (g)

2) Cracking hydrocarbons

………….(catalyst)
C2H6 (g) —-> C2H4 (g) + H2 (g)
ethane –> ethene + hydrogen

Question 4

Chemical reaction for obtaining nitrogen

Answer 4

2H2 (g) + O2 (g) —> 2H20 (l)

Question 5

Step 1 of Haber process

Answer 5

Scrubber: Gasses (nitrogen and hydrogen) are mixed together and scrubbed to remove impurities

Question 6

Step 2 of Haber process

Answer 6

Compressor: Mixture of Nitrogen and Hydrogen is compressed and more mixture of that gas is pumped until the pressure reaches 200 atm.

Question 7

Step 3 of Haber process
reaction
what is the forward reaction
what is the backward reaction
yield

Answer 7

Converter: flows through a round tank with beds of iron catalyst.

N2 (g) + 3H2 (g) ⇌ 2NH3 (g)
—> exothermic
<— endothermic

PER CYCLE yields about 29% ammonia (gas) .

Question 8

What catalyst and temperature in the Haber Process

Answer 8

Iron at 450 deg Celsius

Question 9

Step 4 of Haber process

Answer 9

Cooler: Mixture is cooled till ammonia condenses to a liquid. The excess unreacted nitrogen and hydrogen are recycled and go through the converter again. Step 3 and step 4 occur repeatedly.

Question 10

Step 5 of Haber process

Answer 10

Storage Tanks: liquid ammonia is stored in tanks under pressure.

Question 11

Conditions of the Haber Process
Temperature
Pressure

why

Answer 11

For rate:
Temp - 450 deg Celsius
Catalyst

For yield:
Pressure - 200 atm

Question 12

Why are these conditions chosen for the Haber process

temp - higher and lower
pressure - higher and lower
catalyst

Answer 12

N2 (g) + 3H2 (g) <—-> 2NH3 (g)
—> exothermic
<— endothermic

Temperature:
If lower - yield is higher but reaction takes too much time
if higher - equilibrium would shift to the left and the backward reaction would be favored since its endothermic.

Pressure:
if lower - equilibrium would shift to the left and the backward reaction would be favored since it has more molecules
if higher - it costs a lot to maintain gas at pressure above 200 amu. need powerful pumps and pipes which may burst and need constant maintenance. This costs more and is more unsafe.

catalyst: speeds up reaction

Question 13

Why is the total yield of the Haber process almost 100%

Answer 13

The gas is continually recycled. Designed like this to cope with the low yield of a single cycle in the converter.

Question 14

Is the converter (haber process) a closed system.

Answer 14

No. Molecules ESCAPE and are RECYCLED.

Question 15

Acronym for Haber process

Answer 15

S3S

S(Scrubber), 3Cs, S(Storage)

Question 16

Originally in the Haber process a platinum catalyst was used. Why was it changed to iron?

Answer 16

platinum is expensive