corrosion and transition metals

Question 1

transition metals

Answer 1

sit in the middle on the periodic table

Question 2

physical properties of transition metals

Answer 2

typical properties of a metal

hard, strong, shiny, malleable, conduct heat & electricity, high melting points (except mercury), high densities

Question 3

transition metals and their compounds make good catalysts

Answer 3

a catalyst speeds up the rate of reaction without being changed or used up itself . iron is a catalyst used in the Haber process for making ammonia

Question 4

chemical properties of transition metals

Answer 4

formation of coloured compounds

catalyst activity

Question 5

corrosion

Answer 5

Corrosion happens when a metal reacts with oxygen, making the metal weaker over time. The metal gains oxygen so it oxidises. The corrosion of iron requires water as well as oxygen and is called rusting.

The more reactive a metal is the more rapidly it corrodes.
Gold does not corrode at all. Aluminum is quite reactive so therefore would be expected to corrode quicky. However they don’t because their surfaces form a protective oxide layer (a tarnish) which prevents further reaction.

Question 6

rusting

Answer 6

Rusting is the corrosion of iron and steel (which is mainly iron). Iron rusts when it reacts with oxygen and water.

iron + oxygen + water → hydrated iron(III) oxide

Question 7

rusting prevention

Answer 7

Rusting can be prevented if air is kept away. This can be achieved by storing the metal in an unreactive atmosphere of nitrogen or argon. It can also be prevented if water is kept away, for example using a desiccant powder that absorbs water vapour.

Prevention: 
Painting 
Coating with plastic
Coating with another metal 
Using oil or grease
Store object in vacuum (keep air out) 
Put objects in water containing desiccant

Question 8

Sacrificial protection

Answer 8

Sacrificial protection is a method of rust protection that does not rely on keeping air or water away. Instead a piece of magnesium or zinc is attached to the iron or steel object. Magnesium and zinc oxidize more easily than iron so oxygen reacts with them rather than with the iron or steel object. This protection continues until the sacrificial metal corrodes away. (Can be bolted directly on a ship hull)

Question 9

nail rusting experiment

Answer 9

The experiment in the diagram shows that both oxygen and water are needed for rusting to happen.

The nail only rusts in the left-hand test tube. It does not rust:
in the middle test tube, where there was water but no oxygen
in the right-hand test tube, where there was oxygen but no water