C4- Chemical Changes
- Created by: glory89
- Created on: 29-01-20 10:43
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- C4- Chemical Changes
- Reactions of Metals
- Metal Oxides
- Metals react with oxygen to produce metal oxides
- Most metals are found with oxygen underground
- More reactive a metal is, the more likely it will react
- Gold stays pure while iron doesn't
- Examples:
- Iron Oxide
- Aluminion Oxide
- Copper Oxide
- Redox
- Oxidation
- When a metal reacts with oxygen
- Magnesium is oxidised to make magnesium oxide
- Also the loss of electrons
- The gain of electrons
- Mg has lost 2 electrons, so it has been oxidised
- Reduction
- The loss of oxygen
- Also the gain of electons
- In the equation Cl has gained electrons
- It has been reduced
- In the equation Cl has gained electrons
- OILRIG
- Oxidation is loss
- Reduction is gain
- In terms of electrons
- REDuction and OXidation occurs at the same time
- Oxidation
- The Reactivity Series
- Potassium, Sodium, Lithium, Calcium, Magnesium, Carbon, Zinc, Iron, Hydrogen, Copper, Gold
- Between K and Mg
- All metals are combined with other elements
- Extracted by electrolysis
- The reactivity of a metal depends on its ability to form positive ions
- Between Zn and Cu
- Carbon reduction used to extract metals
- The ore is reduced as oxygen is removed
- Carbon gains oxygen so it is oxidised
- This is because carbon can only take away oxygen from metals less reactive than carbon
- Carbon reduction used to extract metals
- Displacement Reactions
- A more reactive metal will displace a less reactive metal from its compound
- The metal ion will gain ions and reduce
- The metal atom will lose electrons and oxidise
- They are examples of Redox Reactions
- Ionic equations only show the particles that reacts and the products they form
- Iron Extraction
- Haematite- Iron Ore
- Coke- C (solid)
- Limestone- CaCO
- Molten iron falls to bottom as it is dense
- Waste product is molten ****
- Not as dense as iron so floats on top
- Metal Oxides
- Reaction of Acids
- Acids and Metals
- Metal Oxides and Metal Hydroxides
- These are both bases
- The salt that is produced depends on the acid and the metal ion in the oxide or hydroxide
- Metal Carbonates
- These are bases
- Acids and metal carbonates produce carbon dioxide
- Metal Oxides and Metal Hydroxides
- Acids and Bases
- pH scale
- The lower the pH, the more acidic it is
- The higher the pH, the more alkaline it is
- A neutral solution has a pH 7
- Means potential for hydrogen
- pH = -log[H ]
- pH is the measure of concentration of H ions in a solution
- In a strong, monoprotic acid, the [H ]= concentration of the solution
- A strong acid can be dilute (with water)
- A weak acid can be concentration (with water)
- An alkali is a soluble base
- Acids and bases neutralise each other
- Acids forms H ions in water
- They ionise in water
- Alkalis form OH ions in water
- pH scale
- Acids
- Acids produce protons in water
- Strong acids fully ionises in water
- All acids particles dissociates to release H
- Weak acids partially ionises to release H ions in water
- It is a reversible reaction
- It creates an equilibrium
- Titrations
- Used to find out concentration
- Used to find out exactly how much alkali is needed to neutralise a quantity of acid
- It can be the other way
- Burette
- Add KNOWN concentration
- These measure different volumes and let you add the solution drop by drop
- Phenolphthalein Indicator
- Bright pink in alkali, colourless in acid
- Add drops of know solution to conical flask until colour change of at least 10 second
- Conical Flask
- Contains indicator and alkali/acid- unknown solution
- Opposite to what is inside Burette
- Contains indicator and alkali/acid- unknown solution
- Accurate Volumetric Pipette
- Unknown solution to conical flask
- 25cm
- Between 0.05 of all readings
- Do a rough titre first
- Then aim for 3-4 readings
- Concordant Results
- Find results with 0.10 of each other
- This is used to find the concentration
- Making a standard solution
- Weigh 1 mole of a solid
- Transfer to a beaker and dissolve in pure water
- Transfer into 1dm volumetric flask
- Add washings
- Top up to line
- You have made a 1 mol/dm standard solution
- Soluble Salts
- Salts can be made from acids by reacting with solid insoluble substances
- Metals, metal oxides, metal hydroxides or metal carbonates
- The solid is added to the acid until no more reacts and the excess solid is filtered off to produce a solution of the salt
- Salts can be made from acids by reacting with solid insoluble substances
- Acids and Metals
- Electrolysis
- Means separating using electricity
- Very expenisve
- High temperatures
- Electricity costs
- Electrolyte
- A liquid or solution that can conduct electricity
- Electrode
- A solid that can conduct electricity
- The ionic compound must be molten or in solution so that the ions can move
- Electrolysis of Molten Ionic Compounds
- Molten ionic compounds can be electrolysed becasue:
- Ions can move freely
- They can conduct electricity
- Positive metal ions are reduced to the element at the cathode
- Negative non-metal ions are oxidised to the element at the anode
- Molten ionic compounds can be electrolysed becasue:
- General Process
- Positive ions move towards the cathode (-ve electrode)
- They will gain electrons
- They are reduced
- Negative ions move towards the anode (+ve electrode
- They will lose electrons
- They are oxidised
- Electrodes made from graphite due to high temperatures.
- As ions gain or lose electrons, they form atoms
- They will be uncharged elements
- They become discharged from the electroyle
- The flow of charge through the electrolytes as ions travel to the electrodes
- Half Equations:
- Cathode is to push (give electrons)
- Anode is to pull (take electrons)
- Positive ions move towards the cathode (-ve electrode)
- Extracting Metals
- Aluminium is extracted from ore bauxite- aluminium oxide
- Due to high m.p. it is mixed with cryolite to lower it
- If a metal is too reactive to be reduced with carbon or reacts with it, electrolysis is used
- Positive Al ions attract to cathode and reduce to Al.
- They will sink to the bottom
- Negative O will oxidised, and combine to form O
- Equations:
- Aluminium is extracted from ore bauxite- aluminium oxide
- Aqueous Solutions
- The increase of ions allows the electrodes to have a 'choice' of what to oxidise or reduce
- There will be hydrogen ions (H ) and hydroxide ions (OH )
- At Cathode
- If Copper, Silver or Gold?
- If not Hydrogen forms
- Every thing else is too reactive
- At Anode
- Is it a halogen (Group 7)
- If not Oxygen forms
- The increase of ions allows the electrodes to have a 'choice' of what to oxidise or reduce
- Reactions of Metals
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