Topic 5 (lots of questions) Flashcards
Examples of transition metals
Iron, copper, nickel, silver, and gold
Typical properties of transition metals
Malleability, high melting point, good conductor of electricity and heat ,hard,strong,shiny
Which transition metal is liquid at room temperature?
Mercury
Transition metals have high
densities
What is a catalyst
substance that speeds up the rate of a chemical reaction without being changed or used up
Catalyst in haber process
iron to make ammonia
Catalyst in contact process
Vanadium(V) oxide to make sulfuric acid
Transition metals make great
Catalysts
compounds of transition metals are…
colourful. The colour they are depends on the ions they contain
Pure metals are
Malleable due to the regular arrangement so layers can slide over each other. They aren’t useful so some used due to this
What is an alloy
mixture of metals or with a non metal
Why are alloys harder than pure metals?
the different sized atoms of the metals distort the layers in the structure, making it more difficult for them to slide over each other
Steel is…than iron
Harder and stronger as long as carbon is less than 1%
Properties of low carbon steel
easily shaped
Properties of high carbon steel
strong but brittle
Properties of stainless steel
Resistant to corrosion
On its own iron will
Rust/corrode quickly so adding steel helps
Bronze
copper and tin
Brass
copper and zinc
Gold alloys
combining gold with other metals creates the hardness required for an indirect restoration
Aluminium alloys
Used in aircraft as it has the low density of aluminium but is stronger.
Magnalium
aluminium and magnesium
What is a redox reaction?
an oxidation reaction paired with a reduction reaction
Metals can corrode in the presence of
Oxygen and water to form their metal oxides
Corrosion of metals is caused by
Redox reaction s the metal loses electrons so it’s oxidised whilst the oxygen gains electrons when it reacts
Rusting
The corrosion of iron
Experiment for corrosion
Add nail to boiling tube with water and it won’t rust as the boiling water will remove oxygen and oil can be used to stop air getting in. Calcium chloride can be used to absorb any water from the air
How to prevent rusting
Coat the iron with a barrier to keep the water or oxygen out. Eg painting
Preventing rusting on moving parts
Oiling or greasing
Sacrificial protection
Process where a metal is coated with another metal which is more reactive than it,More reactive metal will react with water or oxygen in preference to the less reactive metal
galvanizing
a process in which steel is coated with zinc to prevent corrosion
Electroplating
Coating the surface of a metal with another metal using electrolysis
In electroplating, the cathode is
The object to be plated.
In electroplating, The anode is
Metal sued for plating
Electrolyte in electroplating
A solution containing ions of the coating metal.
Why is electroplating useful?
Household objects like cutlery and cooking utensils are electroplated with metals to stop them corroding. Jewellery is electroplated to improve appearance
Optimum temperature for haber process
450°
Optimum pressure for the haber process
200 atmosphere
Disadvantages of recycling
-can cost more than burying in areas with ample landfill space
Advantages of recycling
Environmentally friendly. Saves money and energy.
equation for haber process
N2 + 3H2 –> 2NH3
Properties of copper
Good electrical and thermal conductor, flexible so used for wiring and pans
Properties of gold
Unreactive so used for jewellery and coins
Uses of aluminium
-Airplane manufacture (light)
What is titration used for?
Finding exactly how much acid is needed to neutralise a given quantity of alkali or vise versa
Titration method
- add set volume of alkali to flask with indicator
unit for concentration
moles/dm3
Formula for concentration
Number of moles (mol) / volume (dm3)
How to convert mol/dm3 to g/dm3
mol/dm3 x Mr of substance = g/dm3
How to find the Mr (relative formula mass) of a substance
Sum of atomic numbers in substance
empirical forumla
a chemical formula giving the simplest whole-number mole ratios of atoms in a compound; also called simplest formula
Yield
The amount of product you get from a reaction. More reactants you start with the more yield you get
Percentage yield formula
actual yield/theoretical yield x 100
What is the theoretical yield
The mass of product you’d make of all reactants were converted to products
How to calculate theoretical yield
-Balance equation
Percentage yield is always
Between 1 and 100. 100 means that all product was delivered but 0 is that none is
In a reaction with a low percentage yield
A lot of reactants are wasted. In industry, we want high yield to limit costs
Ways of not getting 100% yield
Incomplete reactions, practical losses, unwanted reactions
incomplete reaction
If not all of the reactants are converted to product, the reaction id incomplete and the yield will be less
Practical losses
You always lose a bit when you transfer chemicals between containers. Imagine pouring a liquid into a new container - some is always left on the inside of the old one
Unwanted reactions
If unexpected reactions happen, the yield of the intended product goes down, these can be caused by impurities in the reactants or by the change to reaction conditions
A lot of reactions make
More than one product
Some products are
Useful but some are watse
Atom economy
Tells you wha percentage of the mass of the reactants has been converted into your desired product when manufacturing a chemical
Atom Economy Formula
Mr of Desired Product / Mr of All Products x 100
100% atom economy means that…
All the atoms in the reactants have been turned into useful products.
Reactions with low atom economies
Use up resources very quickly. At the same time, they make lots of waste products that have to be disposed which makes the reaction unsustainable because the waste has to go somewhere
Low atom economies aren’t usually
Profitable because materials are expensive and waste is expensive ti remove and dispose responsibly
Way around sustainability of low atom economy reactions
Use the waste products instead of disposing of them so make a reaction that produces by products that could be useful
Atom economy isn the only factor to consider in industry. What else?
Percentage yield, rate of reaction, reaction conditions to move equilibrium for favourable amount of products
Factors to consider when designing an industrial process
- cost of refining and extracting the raw materials will affect whether the process is economically viable to make profit
Haber process equation
N2 + 3H2 –> 2NH3 + heat
Higher pressures in the haber process
Favour the forward reaction because there are gas molecules on the left. The pressure is set to the highest it can be for the haber process to get the best yield but it can’t be too high as it’s too expensive.
Optimum pressure for the haber process
200 atmospheres
Forward reaction in haber process
exothermic so increasing the temperatures decreases the yield of ammonia
Temperature used in the Haber process?
450° because decreasing the temperature decreases the rate of reaction so temperature is increased to have a fast reaction
Catalysts: Haber process
Iron catalyst is used to increase the rate of reaction and so it reaches equilibrium fast too. The catalysts doesn’t affect the % yield or position of equilibrium
3 main elements for a fertiliser
Nitrogen,phosphorous and potassium
Plants absorb
Nutrients from the fertiliser in the soil
If plants don’t get enough essential elements
Their growth and life processes are affected
What do fertilisers do
Supply plants with essential elements that there missing form the soil to increase crop yield by helping the crops grow bigger and faster
advantages of ammonia fertilisers
You can control the compositions of chemicals in them as well as how much is made. Ammonia fertilisers are soluble so all chemicals can dissolve down into the soil to reach the plants.
Ammonia can be reacted with oxygen and water to make
nitric acid
Reacting ammonia with acids
Makes ammonium salts
Ammonia + nitric acid
ammonium nitrate (fertiliser)
How to make ammonium sulfate
Mix ammonia and sulfuric acid in a titration experiment
Ammonium sulfate method
- Set up titration equipment using methyl orange in the ammonia
Industrial production of ammonium sulfate
Ammonia is made using the haber process and and sulfuric acid is made using the contact process. They sue a large reaction chamber filled with ammonia gas and sukfuric acid is sprayed onto the chamber where they produce ammonium sulfate powder
Molar volume
the volume occupied by 1 mole of a gas at standard temperature and pressure (STP); 22.4 L
Molar volume units
dm3 mol-1
Molar Volume Formula
gas volume / number of moles
Avagadro’s Law
under the same conditions of temperature and pressure, equal volumes of different gases contain an equal number of molecules.
at RTP, all gases have the
Same molar volume - 24dm3 mol-1
Molar volume at RTP
Moles x 24
You can use Avogadro’s number to find
Volume of gas a reaction will produce
Chemical cells produce
A voltage across the cell,until all of one of the reactants has been used up
What is a fuel cell?
A type of chemical cell that’s supplied with a fuel and oxygen and uses energy from the reaction between them to produce electrical energy efficiently.
The reaction between hydrogen and oxygen releases
Energy
In a hydrogen oxygen fuel cell
You can produce a voltage (electrical energy) by reacting hydrogen and oxygen and it doesn’t release any nasty pollutants so clean. Releases water
Reaction of a hydrogen-oxygen fuel cell
Hydrogen + oxygen -> water 2H2 + 02 = 2H20
Advantages of hydrogen-oxygen fuel cells
-more efficient
Hydrogen-oxygen fuel cells could replace
Batteries which are highly toxic so dangerous to dispose of
Why won’t hydrogen-oxygen fuel cells take over power stations?
- hydrogen is a gas so takes up more space to store than liquids
What is a mole
the relative formula mass of a substance in grams (6.02 x 10^23)
Number of particles
moles x Avogadro’s constant (6.02 x 10^23)
How to work out molecular formula
Work out the Mr of empirical formula
advantages of hydrogen fuel cells
- do not need to be electrically recharged
Advantages of chemical fuel cells
High emissions
Disadvantages of hydrogen fuel cells
- hydrogen is highly flammable
Advantages of chemical fuel cells
Cheaper
Scale of fertiliser industrial production
Large scale
Starting materials of fertiliser industrial production
Raw materials for ammonia and sulfuric acid (haber and contact process)
Stages of fertiliser industrial production
Several stages
Type of process of fertiliser industrial production
Continuous
Scale of fertiliser lab production
Small scale
Starting materials of fertiliser lab producing
Ammonia solution and sulfuric acid
Stages of lab fertiliser
Titration then crystallisation
Type of process of lab fertiliser
Batch
why is universal indicator not used in titrations?
you want to see a sudden colour change at the end point; U.I turns a variety of colour which indicators a narrow range of pH and is made from a mixture of indicators - it’s a gradual colour change
What is meant by molar volume
Volume that one mole of chemical occupies
How does greasing prevent rusting?
Oil forms a barrier protecting the metal from moisture so it cant rust
What substance prevents corrosion of nail in experiment
Calcium chloride
Why might yield be higher than theoretical
Not all water has been evaporated
How to work out empirical formula from percentages
Moles = mass/mr with mass = the percentages
Explain why a cathode gains mass but anode loses mass
Copper atoms are oxidised at the anode to from positive ions attracted to the cathode but copper ions are reduced at cathode to be attracted to solution
What happens in electrolysis with copper electrolysis
Cations leave the anode and move toward the cathode to be reduced. Anode loses mass and cathode gains mass.
What needs to be remembered about volume for titration
Must be to two decimal places
