Transition metals, alloys and corrosion Flashcards
What are the typical properties of transition metals?
- High melting point.
- High density.
- Form coloured compounds
- Transition metals and their compounds
can be used as catalysts
Which transition metal is used as a catalyst in the
Haber process?
Iron
What causes metals to corrode?
Oxygen reacts with the metal to form a
metal oxide
Why is corrosion of a metal a redox reaction?
The metal loses electrons so is oxidised.
Oxygen gains electrons so is reduced.
What is rusting?
Rusting is the name specifically given to the corrosion of iron when it reacts to oxygen and water in the air.
What two substances need to be excluded to
prevent rusting?
Oxygen (O2)
Water (H2O)
How can oxygen and water be excluded to prevent
iron rusting?
- Paint the metal.
- Coat the metal in oil/grease.
- Cover the metal in plastic.
- Keep the metal in a vacuum container.
What is sacrificial protection? How does it prevent
corrosion?
Sacrificial protection is when the metal being protected from rusting is galvanized with a more reactive metal.
The outer metal will corrode first and will prevent the corrosion of the inner metal.
Which metal is used to in the sacrificial protection of iron?
Zinc
What is electroplating?
A process in which a metal is coated with a layer of another metal.
What are two reasons for using electroplating?
- To make a metal more resistant to
corrosion. - To improve the appearance of a metal
(e.g. silver plated cutlery)
Explain how the process of electroplating works
Similar setup to electrolysis:
The metal being coated is the cathode. The metal that will form the exterior layer is the anode. The electrolyte solution must contain ions of the metal which will form the outer coating. A power supply is connected to both electrodes.
Why are pure metals generally very malleable?
The atoms lie in uniform rows which are
able to slide over one another.
What is an alloy?
An alloy is a mixture of two or more
metals or a metal and another element.
A pure metal can be converted into an alloy. How does this increase the strength of the product?
Alloys contain several metals which will have different sized atoms. This distorts the regular arrangement of the atoms so the layers are unable to slide over one another very easily.
Why is iron alloyed with other metals to produce alloy steels?
Iron is relatively brittle so it is combined with other elements
such as carbon produces a material with more desirable
qualities.
● Low carbon steel: Malleable so used for sheeting.
● High carbon steel: Hard so used for cutting tools.
● Stainless steel: Corrosion resistant so used for cutlery
What property of copper makes it suitable to be used
in electrical cables?
Very good electrical conductor
What property of aluminium makes it suitable for use
in aircrafts?
Low density
What is a key property of gold that makes it suitable
for use in jewellery?
Very unreactive so resist to corrosion.
Jewellery appearance will not be
affected over time.
What is magnalium? What is it used for?
Magnalium is an alloy of magnesium and aluminium. It is lighter and stronger than aluminium and more resistant to corrosion. It is used for car and aircrafts.
What is brass? What is it used for?
Brass is an alloy of copper and zinc.
Brass is hard and resistant to corrosion.
It is used for decorative hardware such
as plumbing fittings.
