C2 Chemical Resources

What is electrolysis?
Electrolysis is the process by which ionic substances are decomposed (broken down) into simpler substances when an electric current is passed through them.
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For electrolysis to work,what must happen?
the ions must be free to move. Ions are free to move when an ionic substance is dissolved in water or when melted. For example, if electricity is passed through molten lead bromide, the lead bromide is broken down to form lead and bromine.
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what happens during electrolysis?(Positive)
Positively charged ions move to the negative electrode during electrolysis. They receive electrons and are reduced.
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What is reduction?
Reduction is the loss of oxygen from a substance.
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What is Oxidation?
Any chemical reaction in which a material gives up electrons, as when the material combines with oxygen. Burning is an example of rapid oxidation; rusting is an example of slow oxidation.
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what happens during electrolysis?(Negative)
Negatively charged ions move to the positive electrode during electrolysis. They lose electrons and are oxidised.
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Electroplating with silver
The object to be plated, such as a metal spoon, is connected to the negative terminal of the power supply. A piece of silver is connected to the positive terminal. The electrolyte is silver nitrate solution.
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Electroplating with copper
The object to be plated, such as a metal pan, is connected to the negative terminal of the power supply. A piece of copper is connected to the positive terminal. The electrolyte is coppersulfate solution.
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Electroplating
Electrolysis is used to electroplate objects. This is useful for coating a cheaper metal with a more expensive one, such as copper or silver.
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Aluminium extraction
The extraction is done by electrolysis. But first the aluminium oxide must be melted so that electricity can pass through it. Aluminium oxide has a very high melting point (over 2000°C) so it would be expensive to melt it. Instead, it is dissolved in
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At the positive electrode
At the positive electrode, negatively charged ions lose electrons. This is oxidation, and you say that the ions have been oxidised. The table summarises some of the elements you should expect to get during electrolysis.
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At the negative electrode
At the negative electrode, positively charged ions gain electrons. This is reduction, and you say that the ions have been reduced.
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The three products of electrolysis
Hydrogen is used as a fuel and for making ammonia...Chlorine is used to kill bacteria in water, and to make bleach and plastics...Sodium hydroxide is used to make soap and bleach
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Al3+ + e– → Al
Al3+ + 3e– → Al
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Cl2+ + e– → Cu
Cu2+ + 2e– → Cu
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Br- → Br2 + e-
2Br- → Br2 + 2e-
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O2- → O2 + e-
2O2 → O2 + 4e-
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Acids
Substances with a pH of less than 7 are acids. Acidic solutions turn blue litmus paper red
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Bases
Substances that can react with acids and neutralise them to make a salt and water are called bases.
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Alkalis
Bases that dissolve in water are called alkalis. Copper oxide is not an alkali because it does not dissolve in water
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Neutral solutions
eutral solutions have a pH of 7. They do not change the colour of litmus paper, but they turn universal indicator paper green. Water is neutral.
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Neutralisation reactions
Ions are charged particles which are formed when atoms, or groups of atoms, lose or gain electrons.
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State symbol(s)
means solid
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State symbol(l)
means liquid
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State symbol(g)
means gas
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State symbol(aq)
means aqueous (dissolved in water)
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Acids Neutralisation
When acids dissolve in water they produce aqueous hydrogen ions, H+(aq). For example, looking at hydrochloric acid:
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Acids Neutralisation Eqaution
HCl(aq) → H+(aq) + Cl–(aq)
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Alkalis Neutralisation
When alkalis dissolve in water they produce aqueous hydroxide ions, OH–(aq). For example, looking at sodium hydroxide:
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Alkalis Neutralisation Eqaution
NaOH(aq) → Na+(aq) + OH–(aq)
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Neutralisation reaction
When the H+(aq) ions from an acid react with the OH–(aq) ions from an alkali, a neutralisation reaction occurs to form water. This is the equation for the reaction: H+(aq) + OH–(aq) → H2O(l)
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Acids and bases
acid + metal oxide → salt + water acid + metal hydroxide → salt + water
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Reactive metals
Acids will react with reactive metals, such as magnesium and zinc, to make a salt and hydrogen: acid + metal → salt + hydrogen
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Naming salts:Chloride
If hydrochloric acid is used.
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Naming salts:Nitrate
If nitric acid is used
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Naming salts:Sulfate
If sulfuric acid is used
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Using precipitation reactions
Precipitation reactions can be used to remove unwanted ions in solution. This is useful for treating drinking water and waste water.
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All nitrates
None
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Most sulfates
Lead sulfate, barium sulfate
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Most chlorides, bromides and iodides
Silver chloride, silver bromide, silver iodide, lead chloride, lead bromide, lead iodide
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Sodium hydroxide, potassium hydroxide
Most other hydroxides
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Making an insoluble salt: Silver nitrate and sodium chloride are both soluble. When you mix their solutions together, you make soluble sodium nitrate and insoluble silver chloride:
silver nitrate + sodium chloride → sodium nitrate + silver chloride AgNO3(aq) + NaCl(aq) → NaNO3(aq) +AgCl(s)
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Ammonia
Ammonia (NH3) is a compound of nitrogen and hydrogen. It is a colourless gas with a choking smell, and a weak alkali which is very soluble in water.
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THe usefulness of Ammonia
Ammonia is used to make fertilisers, explosives, dyes, household cleaners and nylon. It is also the most important raw material in the manufacture of nitric acid
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The Haber process
The raw materials for this process are hydrogen and nitrogen. Hydrogen is obtained by reacting natural gas - methane - with steam, or through the cracking of oil. Nitrogen is obtained by burning hydrogen in air. Air is 80 per cent nitrogen; nearly al
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The reaction is reversible:Nitrogen and hydrogen will react together under these conditions:
N2(g) + 3H2(g) (Equilibrium symbol) 2NH3(g)
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The Miller-Urey experiment - Higher tier
Stanley Miller and Harold Urey carried out some experiments in 1952 and published their results in 1953. The aim was to see if substances now made by living things could be formed in the conditions thought to have existed on the early Earth. The two
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Increasing oxygen
Plants and algae can carry out photosynthesis. This process uses carbon dioxide from the atmosphere (with water and sunlight) to produce oxygen (and glucose). The appearance of plants and algae caused the production of oxygen, which is why the propor
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Decreasing carbon dioxide
Photosynthesis by plants and algae used carbon dioxide from the atmosphere, but this is not the only reason why the proportion of carbon dioxide went down. These processes also absorb carbon dioxide from the atmosphere:
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Liquefying the air
Air is filtered to remove dust, and then cooled in stages until it reaches –200°C. At this temperature it is a liquid. We say that the air has been liquefied.
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Uses of nitrogen and oxygen
liquid nitrogen is used to freeze food...food is packaged in gaseous nitrogen to increase its shelf life...oil tankers are flushed with gaseous nitrogen to reduce the chance of explosion...oxygen is used in the manufacture of steel and in medicine.
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The rate of a reaction
The rate of a reaction can be measured by the rate at which a reactant is used up, or the rate at which a product is formed. The temperature, concentration, pressure of reacting gases, surface area of reacting solids, and the use of catalysts, are al
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How to increase the rate of a reaction
The temperature is increased...The concentration of a dissolved reactant is increased...The pressure of a reacting gas is increased...Solid reactants are broken into smaller pieces...A catalyst is used
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Collisions
For a chemical reaction to occur, the reactant particles must collide. Collisions with too little energy do not produce a reaction.
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Using a catalyst
Catalysts increase the rate of reaction without being used up. They do this by lowering the activation energy needed. With a catalyst, more collisions result in a reaction, so the rate of reaction increases. Different reactions need different catalys
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Other cards in this set

Card 2

Front

the ions must be free to move. Ions are free to move when an ionic substance is dissolved in water or when melted. For example, if electricity is passed through molten lead bromide, the lead bromide is broken down to form lead and bromine.

Back

For electrolysis to work,what must happen?

Card 3

Front

Positively charged ions move to the negative electrode during electrolysis. They receive electrons and are reduced.

Back

Preview of the back of card 3

Card 4

Front

Reduction is the loss of oxygen from a substance.

Back

Preview of the back of card 4

Card 5

Front

Any chemical reaction in which a material gives up electrons, as when the material combines with oxygen. Burning is an example of rapid oxidation; rusting is an example of slow oxidation.

Back

Preview of the back of card 5
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Comments

Alexinnes_

poor effort 

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