Topic 5: Seperate Chemistry 1 Flashcards
What are the transition metals?
Metals in the centre of the periodic table
What are the typical properties of transition metals?
High melting points
High densities
Transition metals and their compounds are good catalysts
Their ions from colourful compounds
What is an alloy?
A mixture of a metal and at least one other element
What is the link between pure metals and malleability? Why
Pure metals are malleable - layers slide over eachother
What is the link between alloys and malleability? Why?
Alloys are stronger than pure metals - not malleable as new elements distort layers of metal atoms so can’t slide past eachother
What are the uses of copper? Why?
Malleable & Corrosion resistance - used in water pipes
Good electrical conductor - used in wiring
What is brass?
The alloy containing copper and zinc
What are the uses of brass?
Shiny and strong - used for decorative taps and door fittings
What are the uses of gold? Why?
Good electrical conductors and corrosion resistant - used in electronic components
Shiny and malleable - used in jewellery
What are the uses of gold alloys?
Jewellery - the gold is strengthened with other metals like zinc, copper or silver
What is steel?
Alloy containing iron and carbon
What are the uses of steel? Why?
Stronger and less likely to rust than iron - used to make long lasting things like bridges and saucepans
What are the uses of aluminium? Why?
Light and soft - used in drinks cans
Good conductor of electricity - used in overhead cables
What is magnalium?
Alloy containing aluminium and around 5% of magnesium
What are the uses of magnalium?
Stronger, lighter and more corrosion resistant than aluminium - used in cars and aeroplanes
What is corrosion?
Damage to metals when they’re oxidised by oxygen and water from their environment
What is rusting?
Corrosion of iron by water and oxygen (from the air)
What happens if a nail is where there is no air but there’s water?
No rust
MUST USE BOILED WATER
POUR OIL ON TOP TO STOP AIR
What happens if a nail is where there is air but there’s no water?
No rust
USE CALCIUM CHLORIDE TO ABSORB WATER
What happens if a nail is where there is air and there’s water?
Rusts
What are the three ways to prevent rusting?
- Barrier methods
- Sacrificial protection
- Galvanisation
What is the barrier method of preventing rusting?
Coating iron to keep out water and oxygen using oil, grease etc.
What is the sacrificial protection method of preventing rusting?
Attaching a more reactive metal which corrodes first to a less reactive metal
What is the galvanisation method of preventing rusting?
Iron is coated with a layer of a more reactive metal like zinc
What is electroplating?
Coating the surface of a metal with another metal using electrolysis
What is the anode in electroplating?
The metal used for electroplating
What is the cathode in electroplating?
The object being electroplated
What happens to the ions of the anode (the metal used for electroplating) in electroplating?
They move to the cathode (the metal that is being electroplated) and are deposited on its surface
What is in the electrolyte for electroplating?
The ions of the metal that is being used for electroplating
What are the uses of electroplating?
Unreactive metals can be coated onto items to prevent corrosion e.g. for cutlery
Precious metals can be coated onto items to improve appearance e.g. for jewellery
What is molar volume?
Volume occupied by one mole of gas
How to calculate molar volume?
Molar volume = volume of gas/number of moles
What is Avogadros Law?
Under the same conditions, all gases will have the same molar volume
What is the molar volume of any gas at room temperature and pressure?
24 dm3 mol−1
What is the the RTP (room temperature and pressure)?
Temperature: 20°C
Pressure: 1 atmosphere
How to calculate the volume of gas produced in a reaction?
- Moles = mass/Ar or Mr of a solid
- Use balanced equation to find number of moles of gas (ratio)
- Volume of gas produced = moles of gas x molar volume
What are the two ways to calculate concentration?
- Concentration = mass of solute/volume of solution
- Concentration = number of moles of solute/volume of solution
What is titration?
Method to find the volume of acid needed to neutralise a given amount of alkali (or vice versa)
What can results of titration be used to calculate?
The concentration of an acid or alkali
How to calculate concentration using titration?
- Multiply known concentration by measured volume to work out number of moles of reactant 1 (measured volume, has a known concentration)
- Use balanced equation (ratio) to work out how many moles of reactant 2 (has a known volume but unknown concentration) have reacted
- Divide number of moles of reactant 2 by its volume to work out unknown concentration
What is yield?
The amount of product made in a reaction
What is percentage yield?
How much product you get (actual yield) compared to how much you’d get if all reactants converted to products (theoretical yield)
How to calculate percentage yield?
Percentage yield = actual yield/theoretical yield X 100
What is the correlation between yield, waste of reactants and costs?
The higher the yield, the less waste of reactants and lower costs
(And vice versa)
Why are percentage yields usually lower than 100%?
- Incomplete reaction - not all reactants converted
- Practical losses - e.g. when transferring product between containers
- Unwanted reactions - reactants don’t make the intended product
What is atom economy?
The percentage of the molecular mass of reactants that gets converted into desired products
How to calculate atom economy?
Atom economy = total Mr of desired products/total Mr of all products X 100
What are the 3 advantages of using reaction with a higher atom economy?
Don’t produce a lot of waste
More profitable
Sustainable
What is the reaction to produce ammonia?
Nitrogen + hydrogen ⇌ ammonia
N2(g) + 3H2(g) ⇌ 2NH3(g)
How is ammonia is produced (process of Haber process)?
- H2 extracted from hydrocarbons and N2 from the air to into the machine (they mix at a ratio of 3:1)
- They go through the reaction vessel passing trays of iron catalyst (pressure is 200 atmospheres and temperature is 450°C)
- Once they’re out, they go through the condenser where ammonia is then removed
- Unused hydrogen and nitrogen are recycled and go through the process again
What does the temperature and pressure have to be in the reaction vessel when making ammonia?
Temperature: 450°C
Pressure: 200 atmospheres
What is the Haber process?
Producing ammonia
What happens to yield and the rate at which equilibrium is reached when temperature is increased in the Haber process?
Yield: lower
Rate at which equilibrium is reached: faster
What happens to yield and the rate at which equilibrium is reached when pressure is increased in the Haber process?
Yield: higher
Rate at which equilibrium is reached: faster
What happens to yield and the rate at which equilibrium is reached when reactant concentration is increased in the Haber process?
Yield: higher
Rate at which equilibrium is reached: faster
What happens to yield and the rate at which equilibrium is reached when a catalyst is used in the Haber process?
Yield: no change
Rate at which equilibrium is reached: faster
What are fertilisers?
Provide extra essential elements to plants to increase crop yields by making them grow faster and bigger
What are the main elements in fertilisers?
Nitrogen, phosphorus and potassium
How are ammonia fertilisers (ammonium nitrate) made?
- Ammonia reacts with oxygen and water to produced nitric acid
- More ammonia is thus reacted with nitric acid to make ammonium nitrate (a fertiliser)
What is the equation of making ammonium nitrate?
NH3(aq) + HNO3(aq) —> NH4NO3(aq)
What are the two types of ammonia fertiliser?
Ammonium nitrate
Ammonium sulfate
How are ammonia fertilisers produced (ammonium sulfate) in laboratory production?
- Titration is done to work out exact reaction quantities
- Mix reactants in exact quantities
- Form crystals by gently evaporation solution using a steam bath then leaving it to cool
How are ammonia fertilisers produced (ammonium sulfate) in industrial production?
Not practical to use burettes and steam baths for large quantities
Several stages required as ammonia and sulphuric acid made from raw materials first
What is a fuel cell?
Chemical cell that uses reaction of fuel and oxygen to produce electrical energy
E.g. hydrogen oxide fuel cells produce a voltage
Advantages of hydrogen-oxygen fuel cells?
Very efficient - electricity is generated directly from reaction so fewer places for energy loss
Clean - don’t produce greenhouse gasses or other pollutants (only water)
Disadvantages of hydrogen-oxygen fuel cells?
H2 is difficult to store - requires a lot of space and is explosive so must be stored safely
H2 has to be produced from either hydrocarbons (non renewable) or water (uses lots of energy)
