Economic importance of iron and cobalt

From pylons to gamma rays

1. Economic importance of the first transition series

2. Iron and cobalt

Iron holds up the power lines outside. A cobalt isotope helps doctors treat tumours. How?

Pick the right answer

Predict: why is cobalt 60 useful in treating tumours?

A. It produces gamma rays with high penetrating power
B. It can be magnetized
C. It is a very hard metal

Explanation

Cobalt 60 is a radioactive isotope of cobalt that produces gamma rays with high penetrating power. That radiation is what reaches the tumour, so cobalt 60 is used in the diagnosis and treatment of tumours.

3. 6- Iron in everyday life

Iron is used in the manufacture of:

Iron is used in the manufacture of
Reinforced concrete
Electricity pylons
Knives
Gun and cannon barrels
Surgical tools

Uses of iron (book p.6)

Look around: the steel rods inside concrete buildings are iron.

4. Iron as a catalyst: Haber-Bosch

Remember: a catalyst speeds up a reaction without being used up.

Iron is used as a catalyst in the manufacture of ammonia by the Haber-Bosch method.

N2 + 3H2 \to[Fe] 2NH3 N X_{2} + 3 H X_{2} Fe 2 NH X_{3}

Iron (Fe) over the arrow is the catalyst; conditions: 500 °C, 200 atm

5. Iron as a catalyst: Fischer-Tropsch

Water gas

A mixture of hydrogen and carbon monoxide.

Water gas ( $H2 H X_{2}$ + CO) → Fuel (Fischer-Tropsch method, Fe catalyst)

Iron also catalyses the conversion of water gas to a fuel

6. Iron check

Pick the right answer

A factory passes a mixture of

H2 H X_{2}

and CO over an iron catalyst. What does it make?

A. A fuel, by the Fischer-Tropsch method
B. Ammonia, by the Haber-Bosch method
C. Water vapour

Explanation

A mixture of

H2 H X_{2}

and CO is water gas. With iron as the catalyst it is converted to a fuel by the Fischer-Tropsch method; the Haber-Bosch method makes ammonia from

N2 N X_{2}

and

H2 H X_{2}

True or false?

Water gas is water in the gas state.

Explanation

Water vapour is

H2O H X_{2} O

as a gas. Water gas is a mixture of hydrogen and carbon monoxide (

H2 H X_{2}

+ CO), and iron catalyses its conversion to a fuel (Fischer-Tropsch method).

7. 7- Cobalt: magnets and batteries

Cobalt is similar to iron: both of them can be magnetized. So they are used in the manufacture of magnets.

Iron → Can be magnetized
Cobalt → Can be magnetized
Can be magnetized → Magnets (so)

Cobalt is similar to iron: both can be magnetized (book p.7)

Cobalt is also used in the manufacture of modern dry batteries used in cars.

8. Cobalt 60 and gamma rays

Cobalt has twelve radioactive isotopes. Cobalt 60 is very important because it produces gamma rays with high penetrating power.

Gamma rays of cobalt 60 are used in
Food preserving
Detecting the quality of industrial products
Detecting cracks and welding connections
Medicine: diagnosis and treatment of tumours

Uses of cobalt 60 (book p.7)

True or false?

Cobalt 60 is used in treating tumours because cobalt can be magnetized.

Explanation

Cobalt 60 is used in treating tumours because it produces gamma rays with high penetrating power; cobalt being magnetizable is the reason it is used in magnets.

9. Iron or cobalt?

Sort into groups

Sort each use by the element.

Electricity pylonsCatalyst in making ammoniaModern dry batteries used in carsDetecting cracks and welding connectionsSurgical toolsConverting water gas to a fuel

Pick the right answer

Mangoes are treated with gamma rays from cobalt 60 to preserve them. A buyer asks: "Are they radioactive now?" The best reply is:

A. No. The rays pass through; the food does not become radioactive
B. Yes, but only for a few days
C. No, because cobalt is magnetic

Explanation

The gamma rays from cobalt 60 pass through the mangoes. The radioactive isotope stays in the source and does not get into the fruit, so the mangoes do not become radioactive.

10. Summary

Back to the hook: cobalt 60 treats tumours because its gamma rays have high penetrating power.

	Iron (Fe)	Cobalt (Co)
Used in the manufacture of	reinforced concrete, electricity pylons, knives, gun and cannon barrels, surgical tools	magnets (like iron), modern dry batteries used in cars
Special use	catalyst: ammonia (Haber-Bosch method); water gas ( $H2 H X_{2}$ + CO) to a fuel (Fischer-Tropsch method)	cobalt 60: gamma rays with high penetrating power (food preserving, quality of industrial products, cracks and welding connections, tumours)

Economic importance of iron and cobalt (book pp.6-7)

Can you explain why gamma-treated food is not radioactive?

Concepts in this lesson