Separate Chemistry 1 Flashcards
What are the typical properties of transition metals?
- High melting point (except mercury)
- High density
- Stronger and harder than the metals in group 1 and 2 (often used for construction )
- Formation of coloured compounds
- Catalytic activity
What is a catalyst?
- Increase the rate of a chemical reaction
- Without altering the products of the reaction
- Without changing chemically
- Without changing in mass at the end of the reaction
What are the properties of group 1 and 2 elements?
- Relatively low melting point
- Relatively low density
- Formation of white or colourless compounds
- Lack of catalytic activity
What are the reasons for not obtaining the theoretical yield?
- Incomplete reactions – reaction hasn’t finished, reaction reaches equilibrium
- Side reactions – competing, unwanted reaction is so bi-products are also made
- Practical losses – losses during purification (e.g. filtration), losses during transfers (e.g. liquid left behind in containers)
What is atom economy?
A way of measuring the number of atoms wasted when making a substance
How can rusting be prevented using physical barriers?
- Painting
- Using oil or grease
- Coating with plastic
- Coating with another metal
How would you carry out a rusting experiment?
- Place a nail in a test tube with air and water
- Place a nail in a test tube filled with water with a layer of oil on top
- Place a nail in a test tube with calcium chloride (which absorbs water)
- Only the nail with water and air will rust
How does electroplating work?
- Electrolysis is used to put a thin layer of metal on the object
- The cathode is the iron or steel object
- The anode is the plating metal
- The electrolyte contains ions of the plating metal
What is it sacrificial protection?
If iron is in contact with a more reactive metal (zinc), the more reactive metal oxidises more readily than the iron so it ‘sacrifices’ itself
How does galvanising prevent iron from rusting?
- The zinc layer stops oxygen in water reaching the iron
 - The zinc is more reactive than iron so it also acts as a sacrificial metal
- This means the protection works even if the zinc layer is scratched
Why are alloys often stronger than pure metals?
- Pure metals have a regular lattice structure with layers that slide over each other
- Alloys have different sized ions that disrupt the regular structure and prevent it from sliding easily
What are some examples of alloy steels?
Mild steel (carbon) – malleable, ductile
Tool steel (tungsten) – hard, resistant to high temperatures
Stainless steel (chromium) – hard, resistant to rusting
What are the properties of aluminium?
- Low density, used for aircraft
- Does not react with water, used as foil for storing food
- Malleable, **
What are the properties of copper?
- Resists corrosion
- Good electrical conductors, used in wires
What are the properties of gold?
- Resists corrosion and stays shiny, used for jewellery