Topic 5 Flashcards
Done except for a few specpoints
5.1
Where are transition metals found in the periodic table?
In the middle
5.1
What are the properties of transition metals?
-↑ densities
-↑ mp & bp
-Good electrical conductors
-Form coloured compounds
-Have variable oxidation states (lose diff no. of e⁻)
5.1
Explain why transition metals typically have high melting and boiling points
-Strong electrostatic forces of attraction between oppositely charged cations & e⁻
-Lot of energy needed to overcome these forces
5.1
Explain why transition metals typically have high densities
Cations closely packed together
5.1
Explain why transition metals are good electrical conductors
-Release outer shell e⁻ to form metal ions in sea of delocalised e⁻
-e⁻ free to move + carry charge
5.2
Define the term corrosion
Oxidation of metal
5.2
Why do objects made of aluminium not corrode as much as expected?
-Al reacts rapidly w/ O₂ bc very reactive -> forms aluminium oxide layer
-Layer is unreactive -> will no longer react -> resistant to further corrosion
5.3
How can rusting of iron be prevented?
-Exclusion of oxygen
-Exclusion of water
-Sacrificial protection (galvanising)
5.3
3 nails are left in contact with air and water for a few days. The nail wrapped in magnesium does not rust. The nail alone rusts but the nail wrapped in copper rusts more. Explain these observations.
-Mg more reactive than Fe
-Mg oxidises more readily
-Nail doesn’t rust
-Fe more reactive than Cu
-Fe oxidises more readily
-So Cu rusts faster than nail alone
5.4
What is electroplating?
Coating 1 metal object with another
5.4
How does electroplating work?
-Electric current passed through solution
-Cathode = iron/steel object
-Anode = plating material
-Electrolyte = contains ions of plating material
5.4
How would you electroplate silver onto copper?
-Ag atoms lose e^- -> Ag+ ions
-Ag+ ions go into electrolyte -> migrate to negative Cu ring
-Ag+ ions gain e^- -> Ag atoms
5.4
What is the purpose of electroplating?
-Improve aesthetic
-Improve resistance to corrosion of metal objects
5.5
Define the term alloy
Mixture of metals
5.5
Explain why alloying increases the strength of the pure metal [3 marks]
-Pure metal: atoms = same size
-So atoms can move/slide easily within LAYERS
-Alloy: atoms = diff sizes
-Prevents layers from sliding
5.7
State 2 uses of aluminium and the properties that make it suitable for that use
Aeroplanes + cars
-Low density
Drink cans
-Resistant to corrosion
5.7
State 2 uses of copper and the properties that make it suitable for that use
Electrical cables
-Good electrical conductor
Water pipes
-Resistant to corrosion
5.7
State 2 uses of gold and the properties that make it suitable for that use
Jewellery
-Unreactive -> doesn’t corrode
-Attractive
Circuit boards in phones
-Good electrical conductor
5.8
Convert 1dm³ into cm³
1000cm³
5.8
State 2 equations to calculate concentration in mol dm³
=amount of solute in mol/v of solution in dm³
(c=n/v)
=concentration in gdm³/ Mr of solute
5.8
Calculate the volume of solution, in cm³, containing 0.005 mol of potassium chloride that will have a concentration of 5.0 mol dm³
v=n/c
=0.005/5
=0.001dm³
=1cm³
1cm³
5.10
See freescience lessons vid on titration calculations
-
5.11
State the equation for percentage yield
-Percentage yield = actual yield/theoretical yield x100
(%y = acc/theo x 100)
5.12
Define the term theoretical yield
Max mass of product that can be formed from given amount of reactant
5.12
Define the term actual yield
Actual m of product formed
5.12
The percentage yield of a reaction is usually less than 100% because the actual yield tends to be less than the theoretical yield. Explain why this is
-Incomplete reactions
-Practical losses during experiment
-Competing side reactions
5.13
Define the term atom economy
Shows %, by mass, of useful products formed in reaction
5.14
State the equation for atom economy
Mᵣ of useful product/Mᵣ of all reactants
x100
5.14
In what situation can an atom economy of 100% be obtained?
-If only 1 product formed & it = useful
-e.g. 2H₂ + O₂ -> 2H₂
5.14
Explain a reason for why a low atom economy is a disadvantage in a manufacturing process
-Produce waste products
-May be toxic/corrosive-> difficult/expensive to dispose of
5.14
State how the atom economy can be improved
Find uses for waste products
5.16
State the equation used to work out the amount of gas (mol)
=volume of gas (dm³)/molar volume (dm³)
(n=v/V little m)
Assume Vm = 24dm³ unless stated otherwise
5.16
What is the molar volume of any gas at room temperature?
24dm^3
5.19
What is the Haber Process?
Reversible reaction between nitrogen & hydrogen to form ammonia
5.19
What does the rate of reaction mean?
How fast/slow reaction occurs
5.19
See book for rate graphs
-
5.20
State 5 factors affecting the rate of reaction
-Concentration
-Temperature
-Pressure (of gases)
-Catalysts
-SA of one of reactants
5.20
Explain how increasing the temperature affects the rate of reaction [3 marks]
-Hotter particles-> gain more KE -> faster
-More frequent, successful collisions between particles in given t
-Increases
5.20
Explain how increasing the pressure affects the rate of reaction [3 marks]
-As pressure increases, space in which gas particles move in becomes smaller
-More frequent, successful collisions between particles in given time
-Increases
5.20
Explain how increasing the concentration affects the rate of reaction [2 marks]
-More particles in same VOLUME
-More frequent, successful collisions between particles in given time
-Increases
5.20
Describe the effect of increasing the pressure on the movement of particles and the time taken for equilibrium to be reached
-Equilibrium position moves in direc that produces less gas (fewest molecules)
-Time decreases
5.20
Describe the effect of increasing the concentration on the movement of particles and the time taken for equilibrium to be reached
-Equilibrium position shifts AWAY from that reactant
-Time decreases
5.20
Describe the effect of increasing the temperature on the movement of particles and the time taken for equilibrium to be reached
-Equilibrium position shifts in direc of endo reaction
-Time decreases
5.20
Describe the effect of adding a catalyst on the equilibrium and the time taken for equilibrium to be reached
-Increases r. reaction
-But no change in equilibrium position
-Time decreases
5.21
In industrial reactions e.g. the Haber process, what is considered when choosing the conditions?
The availability & cost of:
-Raw materials
-Energy
-Supplies
5.22
What are fertilisers?
-Replace mineral ions
-Promote plant growth
5.22
State the 3 main elements found in fertilisers
-Nitrogen
-Phosphorus
-Potassium
(N,P,K)
5.22
State the formula for
a) Ammonia
b) Ammonium
a) NH₃
b)NH₄
5.23
What fertiliser is produced in the reaction between ammonia and nitric acid?
Then give the balanced chemical equation for this reaction
-Ammonium nitrate
-NH₃ (aq) + HNO₃ (aq) -> NH₄NO₃ (aq)
5.23
Work out the formula for the fertiliser ammonium phosphate
(NH₄)₃PO₄
Help: (NH₄^+ PO₄^3-
1 3)
5.24a
Describe the laboratory preparation of producing the fertiliser ammonium sulfate
-Small scale
-Starting materials: Ammonia solution & dilute sulfuric acid
-Stages: Titration then crystallisation
-Type of process: Batch
5.24b
Describe the industrial production of producing the fertiliser ammonium sulfate
-Large scale
-Starting materials: Raw materials for making ammonia & sulfuric acid
-Stages: Several
-Type of process: Continuous
5.25
What is a battery?
2/more electrical cells joined together
5.25
Name the 2 types of electrical cells
-Chemical cells
-Fuel cells
5.25
What are chemical/electrical cells?
Use chemical reaction to produce electricity
5.25
Explain which cell, made from the following combinations of metals and their salt solutions, will produce the greatest voltage:
-Magnesium & zinc
-Magnesium & copper
-Zinc & copper
-Mg & Cu
-The further away the metals are from each other in the reactivity series, the greater the voltage
5.26
Describe and explain what happens (the reaction) in a hydrogen-oxygen fuel cell. Give the balanced chemical equation
-Hydrogen + Oxygen react to produce VOLTAGE
-Anode: oxidation
-H₂ atoms lose e^- -> H₂ ions
-2H₂ (g) -> 4H^+ (aq) + 4e
-Cathode: reduction
-H₂ ions & e^- react w/ O₂ to form water
-4H^+ (aq) + 4e + O₂ (g) -> 2H₂O (l)
-Water = only product
-2H₂ (g) + O₂ (g) -> 2H₂O (l)
5.27
Discuss the advantages and disadvantages of using hydrogen rather than diesel as a fuel for vehicles
Adv
-Only water produced (harmless/no GHG)
-Raw material for production of H₂ is water -> renewable/plentiful supply
Dis
-H₂ difficult to store bc needs to be under pressure
-Difficult to transport bc gas leaks (flammable)
-CO₂ produced in manufacture & storage & transport
-Few H₂ refuelling stations
-More expensive
5.27
What are 3 advantages of using fuel cells in spacecraft?
-Lightweight
-Small for amount of electricity they produce
-No harmful emissions
5.27
Why do spacecrafts have 2 sources of energy they interchange between and what are they?
-Hydrogen & solar
-Hydrogen fuel cells supplied w/ H₂ & O₂
-Could be problem when leave Earth
-So have solar cells
-Convert light -> electricity
-But only works when in light
-Ensures reliable power supply
eDescribe how you could prepare a pure solution of ammonium chloride in the laboratory
-Ammonia solution in beaker
-Add indicator (e.g. universal indicator)
-Add HCl until solution just changes colour
Iron fences can be galvanised with a layer of zinc. When this layer is scratched, exposing the iron, the iron does not rust. Explain why
-Zn corrodes instead
-Bc it is more reactive
