Separate Chemistry 1 Flashcards
(34 cards)
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
What are the properties of magnalium (aluminium + magnesium) ?
- Low-density and stronger than aluminium, used in cars and planes
What are the properties of brass (copper + zinc) ?
- Hard, resistant to corrosion, still conducts electricity, used for the pins in electrical plugs
What is the equation for concentration?
Concentration (mol dm^-3) =
Amount of solute (mol)
/
Volume of solution (dm^3)
How do you calculate the percentage yield?
Actual yield / Theoretical yield
x
100
How do you calculate atom economy?
Total Mr of desired products /
Total Mr of all products
x
100
When is the atom economy 100%?
- If there is only one product
- All of the byproducts are used
What should you look for when explaining why particular reaction pathway is chosen?
- High atom economy
- High yield
- Fast rate
- Equilibrium position to the right
- Useful byproducts
What is Avogadro’s law?
Equal volumes of different gases contain an equal number of molecules
When temperature and pressure stay the same
What is molar volume?
The volume occupied by one mole of molecules of any gas at room temperature and pressure
