Topic 5 - separate chemistry 1 Flashcards
What are the typical properties of transition metals?
High melting point
High density
Form coloured 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 and the oxygen gains electrons so is reduced.
What is rusting?
The name specifically given to the corrosion of iron when it reacts to oxygen and water in the air
What two substances nwe’d to be excluded to prevent rusting?
Oxygen and water
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?
When the metal being protected from rusting is galvanised with a more reactive metal.
The outer metal will corrode first and will prevent the corrosion of the inner metal.
Which metal is used 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
Explain how electroplating works
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?
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.
Allows 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 quite brittle so it is combined with other elements such as carbon which produces a metal with more desirable qualities
What are the desirable qualities of low carbon steel, high carbon steel and stainless steel?
LCS: Malleable so used for sheeting
HCS: hard so used for cutting tools
SS: Corrosion resistant so used for cutlery
What property of copper makes it suitable to be used in electrical cables?
It is a very good electrical conductor
What property of aluminium makes it suitable for use in aircrafts?
It has a low density
What is a key property of gold that makes it suitable for use in jewellery?
It is very unreactive so resistant to corrosion
Jewellery appearance will not be affected over time
What is magnalium?
An alloy of magnesium and aluminium
What are the desirable qualities of magnalium?
It is lighter and stronger than aluminium and more resistant to corrosion
What is magnalium used for?
Cars and aircrafts
What is brass?
An alloy of copper and zinc
What are desirable qualities of brass?
It is hard and resistant to corrosion
What is brass used for?
Decorative hardware such as plumbing fittings
How do you calculate the concentration of a solution in mol dm-3?
Concentration (mol dm-3) = moles /volume (dm3)
How can you convert concentration in g dm-3 to mol dm-3?
Concentration (mol dm-3) = concentration (g dm-3)/ molecular mass
Describe how to carry out and acid-alkali titration to find the concentration of alkali
- Rinse the Pipette with the solution of unknown concentration (alkali). Use this Pipette to add a known volume of alkali to a conical flask
- Add a few drops of indicator
- Rinse and fill the Barette with acid
- Gradually add the acid to the conical flask
- Record the volume in the Barette when the indicator changes colour
- Repeat the experiment until you have concordant results
- Use results to calculate a mean titre and the concentration of alkali