SC10/11/12/13: Electrolysis, Transition Metals & Alloys Flashcards
SC10a Electrolysis
A) What is eletrolysis?
B) What are electrolytes?
A) This is the process of using electricity to break down electrolytes to from elements. ( Also decomposes electrodes )
B) These are ionic substances with freely moving ions which allow them to conduct electricity.
SC10a Electrolysis
Describe the movement of;
A) Cations
B) Anions
In electrolysis.
A) Cations are positive ions and are attracted to the negative Cathode.
B) Anions are negative ions and are attracted to the positive Anode.
The Metal is produced at the Cathode and the Non-metal at the anode.
SC10b Products from electrolysis
Describe the electrolysis of Copper Chloride in water.
1. Ions -> Cu2+ and Cl- ( from salt ), H+(aq) and OH- ( from water ).
2. Cathode - Cu2+ and H+ are attracted to the Cathode, Cu2+ ions are discharged more readily than H+ ions, so copper is formed as a brown solid.
3. Anode - Cl- and OH- are attracted to the Anode, Cl- ions are discharged more readily than OH- ions, so cholrine is formed as a pale green gas.
4. Overall - The copper chloride decomposes and the water doesn’t change.
SC10b Products from electrolysis
Describe the electrolysis of Sodium Cholride in water.
1. Ions -> Na+ and Cl- ( from salt ), H+(aq) and OH- ( from water ).
2. Cathode - Na+ and H+ are attracted to the Cathode, H+ ions are discharged more readily than Na+ ions, so hydrogen gas is formed.
3. Anode - Cl- and OH- are attracted to the Anode, Cl- ions are discharged more readily than OH- ions, so cholrine is formed as a pale green gas.
4. Overall - Sodium chloride decomposes to form hydrogen and cholrine. The sodium and hydroxide ions remain in the solution.
SC11a Reactivity
Describe the reactivity series in reference to the metals and their reactions with;
A) Water
B) Dilute acid
Order is; potassium, sodium, calcium, magnesium, aluminium, zinc, iron, copper, silver, gold.
- ( In decreasing reactivity )
A) Water/Steam
- React to form hydrogen & a metal hydroxide; Pot, Sodium & Calcium
- React very slowly with steam to form hydrogen & metal oxide; Mag, Al, Zinc, Iron
- The rest don’t react at all.
B) Dilute acid
- React violently; Potassium & Sodium
- React to form hydrogen & a salt solution; Cal, Mag, Al, Zinc, Iron
- The rest don’t react at all.
SC11b Ores
Evaluate the following method of Extraction;
A) Bioleaching
B) Phytoextraction
A) Bioleaching - Uses bacteria grown on low grade ore, the bacteria produces a solution containing the metal’s ions called leachate.
Advantages;
- Doesn’t require high temperatures
Disadvantages;
- Toxic substances and sulfuric acid can be produced by the process, and damage the environment.
B) Phytoextraction - Involves growing plants that absorb metal compounds, the plants are burnt to form ash, from which the metals extracted.
Advantage;
- Can extract metals from contaminated soils
Disadvantages;
- More expensive than mining some ores
- Growing plants is dependant on weather conditions
Both
Advantges;
- No harmful gases ( e.g. sulfure dioxide ) are produced
- Causes less damage to landscape than mining
- Conserves supplies of higher grade ores.
Disadvantge;
- Very slow
SC11d Life cycle assessment and recycling
Explain the advantages & disadvantages of recycling metals
Advantages;
- Natural reserves of metal ores will last longer
- The need to mine ores is reduced. Mining can damage the landscape as well as create noise and dust pollution
- Less pollution may be produced. For exampl, SO2 is formed when some metals are extracted from metal sulfide surfaces
- Many metals need less energy to recycle them than to extract new metal from the ore.
- Less waste ends up in landfill sites
Disadvantages;
- It can sometimes be more expensive & require more energy, to recycle rather than extract a new metal.
SC11d Life cycle assessment and recycling
Describe the 4 stages of the Life cycle assessment & the use of a LCA.
4 Stages;
- Obtaining and processing raw materials
- Manufacturing and packaging the product
- Using the product
- Disposal of the product
Uses;
- Can be carried out to work out the environmental impact of a product.
- Can also be used to decide whether it’s worthwhile to manufacture and recycle a product
- LCA’s can be used to compare the effect of using different materials for the same product.
SC12a Dynamic Equilibrium
A) Describe what is ment by Dynamic Equilibrium
B) What conditions does the Haber process occur under
A) During a reversible reaction, there will be a certian point at which the forward reactions and backwards reactions will be occuring at the same speed, this is dynamic equilibrium.
- These can only occur in closed systems.
B) Conditions;
- Temperature 450C
- Pressure 200 atmospheres
- Iron catalyst
SC12a Dynamic Equilibrium
Describe how the position of Equilibrium changes with;
A) Temperature
B) Pressure
C) Concentration
A) Temperature
- Increasing temperature shifts equilibrium in the endothermic direction
- Decreasing temperature shifts equilibrium in the exothermic direction
B) Pressure
- Increasing pressure shifts equilibrium in the direction that forms fewer gas molecules.
- Decreasing pressure shifts equilibrium in the direction that forms more gas molecules.
C) Concentration
- Increasing concentration shifts equilibrium in the direction that uses up the substances that have been added.
- Decreasing concentration shifts equilibrium in the direction that forms the substances that have been removed.
SC13a Transition metals
Describe the common features of a transition metal
- Malleable ( they can be hammered or rolled into shape without shattering )
- Ductile ( They can be stretched out to make thin wires )
- Good conductors of electricity
- Shiny
- Usually coloured
- Typically show catalytic activity
- High melting points ( When compared to group 1 & 2 metals )
- High densities ( When compared to group 1 & 2 metals )
SC13b Corrosion
Describe what corrosion is and how it is/can be prevented.
1. Corrosion: When metals react with oxygen in the air, they oxidise to form metal oxides.
- Metals oxidise when they lose electrons.
2. Metals may form a thin layer of tarnish when they oxidise.
- This layer stops oxygen reaching the metal, preventing further oxidation.
SC13b Corrosion
Describe;
A) What rusting is
B) The different ways of preventing rusting
A) Rusting is the corrosion of iron or steel. Iron rusts when it reacts with oxygen and water.
B) Some ways of preventing rusting are;
- Keeping the air away from the Iron. This can be achieved by storing the metal in an unreactive atmosphere like argon.
- Keeping the water away from the Iron, for example using a desiccant powder that absorbs water vapour.
- Sacrifical Protection: By attaching a more reactive metal ( e.g. magnesium ) to the Iron, it will cause that metal to be oxidised instead of the iron, preventing rust build up.
SC13c Electroplating
Describe what Electroplating is and some reasons why it may be used.
- Electoplating is the process of coating the surface of one metal with a thin layer of another metal.
- One reason Electroplating may be used is to improve the appearence of the object. ( Gold/Silver/Chronium could be used )
- Another reason is to improve a metal’s ability to resist corrosion. ( Steel could be electroplayed with Chronium to help it resist corrosion )
SC13c Electroplating
Describe how electroplating could be carried out to coat a copper ring in silver.
To electroplate a metal you would need:
- An anode, made from the plating metal
- An electrolyte, which is a solution containing ions of the plating metal
- A cathode, which is the metal object being plated.
Process:
- As a D.C flows through the electrodes, the silver atoms at the electrode lose electrons to become silver ions which move into the electrolyte.
- The silver ions then move to the cathode ( Copper ring ) where they gain the electrons previously lost and are then deposited as silver atoms on the gold ring.
SC13c Electroplating
Describe what;
A) Galvanising
B) Tin plating
is.
A) Iron & Steel object can be protected from rusting by covering them in zinc, this is called galvanising.
- Thin layer of zinc improves corrosion resistance by preventing water from reaching the metal.
- It will also act as sacrificial protection that can continue even if zinc is damaged.
B) Food cans are made of steel. Their inner surface is protected from rusting by electroplating with tin.
- Tin does not react with air or water at room temp. If the tin layer is damaged, the steel can will rust faster.
- This is because iron is more reactive than tin. ( Steel is made of Iron & Carbon )
SC13d Alloying
A) What is an alloy?
B) Explain why alloying increases the strength of the product.
A) An alloy is a mixture of metal element with one or more other elements, usually metals.
B) In a solid, pure metal the atoms are all the same size and are regularly arranged into layers.
- These layers move past eachother if enough force is applied. ( This is what makes metals malleable & ductile )
- However, in an alloy the atoms may be of different sizes, making it harder for the layers to slide over eachother. This makes the alloy stronger.
SC13d Alloying
Explain why iron is alloyed with other metals to produce alloy steels.
- Pure iron is to soft for every day use, so by alloying it, it makes the metal much stronger.
- Stainless steels resist rusting, unlike other alloy steels and iron. Stainless steels contain chromium, which reacts with oxygen in the air.
- A layer of chromium oxide forms that is thick enough to prevent water/oxygen from reacting with the metal below, but thin enough to be transparent.
SC13e Uses of metals and their alloys
Explain how the properties of; Aluminium, Gold & Copper are related to their use.
- Aluminium resists corrosion, but it does not conduct electricity as well as copper. However it is stronger, cheaper and less dense so it is used for overhead wiring.
- Gold and copper both resist corrosion. They are also malleable, ductile and good electrical conductors. Both could be used for wiring but Gold is thousands of times more expensive than copper.
- So copper is used for electrical wiring while Gold is used in tiny amounts to connect microprocessors and memory chips.
SC13e Uses of metals and their alloys
Explain how the properties of; Magnalium & Brass are related to their use.
- Brass is an alloy of Copper and Zinc. Copper and Brass both resist corrosion. While copper is a better electrical conductor than brass, brass is stronger. This makes brass more suitable for making electrical plug pins.
- Magnalium contains 95% aluminium and 5% magnesium & is used in aircraft parts and scientific instruments. Magnalium is less dense than aluminium while still being almost 4x stronger.
- Although Magnalium is more dense than magnesium, it is 2x as strong and has better resistance to corroding. These properties allow magnalium to be strong but light weight.
