CHEMISTRY
Topics
Production of MaterialsShipwrecks and Salvage (Option)
The Acidic Environment
Chemical Monitoring and Management
Notes about these Notes
Some of these notes may be out of order and in the wrong section. It is best to search for keywords through to find what you need.Some of these notes may also be incorrect. Check your facts.
Production of Materials
Title: 16 October 2007 Chemistry
Date: 16 October 2007 6:28 PM
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1.2 Ethelyne
Ethene: C2H4
Common name Ethylene
Produced from natural gas or crude oil.
To refine petroleum, distil it.
2 ways of producing ethene:
1. Catalytic Cracking
2. Steam Cracking
Cracking is breaking the larger less usable hydrocarbons into more usable smaller ones.
1. Cracking decane into octane and ethene
C10H22 (g) → C8H18 (g) + C2H4 (g)
Catalytic cracking involves zeolites which bash the hydrocarbon chains. The zeolites are a type of catalyst.
2. A type of thermal cracking. The major source of ethene in the industry.
Ethane is fed into furnaces of steam.
C2H6 (g) → CH2=CH2 (g) + H2 (g)
Propane works too
C3H8 (g) → CH2=CH2 (g) + CH4 (g)
The double bond in the ethene makes it more reactive.
An addition reaction occurs when an alkene reacts and gains 2 atoms.
When applied to ethene they are called:
- Hydrogenation (H2 added)
- Halogenation (Halogen added eg Cl2)
- Hydrohalogenation (eg HCL)
- Hydration (Water added)
Title: 17 October 2007 Chemistry
Date: 17 October 2007 7:10 PM
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Alkenes
A characteristic of these is that that they do addition reactions.
2 new atoms are added across the double bond. Converting a unsaturated bond to a saturated one.
- Hydration
- Hydrogenation
- Halogenation
- Hydrohalogenation
Sheets. More stuff.
Title: 19 October 2007 Chemistry
Date: 19 October 2007 11:21 AM
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Polymerisation
Where monomers become linked to form polymers by way of chemical reactions.
1. Addition polymerisation
Monomers simply add together to form a chain. Involve unsaturated monomers.
2. Condensation Polymerisation
Involves reaction between 2 functional groups where a molecule is eliminated (like water). The functional groups are then linked. Most common in carboxylic acid (COOH) and alcohol (OH) or amine group (NH2)
Title: 23 October 2007 Chemistry
Date: 23 October 2007 6:20 PM
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1.5 Identify polyethylene as an addition polymer and explain the meaning of this term.
1.6 Outline the steps in the production of polyethylene as an example of a commercially important polymer.
1.7 Identify the following as commercially important monomers: vinyl chloride (chloroethene), styrene (phenylethene) by both their common and systematic names.
1.6 Liquid ethene under huge pressure is heated in the presence of a catalyst to form polyethylene.
Low Density PolyEthelyne is low density and has low dispersion forces. Thermoplastic
High Density PolyEthelyne is high density, harder and stronger.
Title: 25 October 2007 Chemistry
Date: 25 October 2007 8:45 PM
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Prac
Model polymers with Molymod kits.
Modeled Ethene thene polyethylene. Modeled vinyl chloride (chloroethene) then poly(vinyl chloride)
Title: 26 October 2007 Chemistry
Date: 26 October 2007 5:34 PM
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Discuss the need for alternative sources of compunds presently obtained from the petrochemical industry
Running out of compounds that nturally occur in the earth. We will run out and be left with nothing. Plants could be an alternative.
Explain what is meant by a condensation polymer
A polymer that forms when monomers bond. A functional group from one monomer bonds with another functional group from another monomer and they are eliminated.
Define the term Biomass
Things produced by living organisms eg plant matter, excretions etc.
Justify that Cellulose is a major component of Biomass
It's true
Identify that cellulose contains the basic carbon-chain structures needed to build petrochemicals and discuss its potential as a raw material.
Glucose can be formed from cellulose which can be fermented into ethanol which is a fuel
Title: 30 October 2007 Chemistry
Date: 30 October 2007 6:16 PM
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Cellulose: Polysaccharides (yeast is one too)
Biopol®
Biopolymer. Biodegrades relatively easily. Can be grown through E.Coli and genetic engineering instead of just bacteria that produces the monomers.
Title: 31 October 2007 Chemisty
Date: 31 October 2007 8:46 PM
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- Alcohols are a carbon compounds with OH group
- Alkanols are a type of alcohol where 1 or more H in an alkane are replaced by OH
- They dissolve (polar)
- Solubility decreases with more chain length
- OH group causes hydrogen bonding so higher boiling points
- 3 types of alcohols: primary secondary and tertiary.
Types
- Primary: The Carbon that the OH is bonded to is also bonded with two atoms that aren't carbon
- Secondary: The Carbon that is bonded with the OH is also bonded with one atom that isnt carbon
- Tertiary: The Carbon that the OH is bonded to is also bonded to 3 Carbons
Title: 2 November 2007 Chemistry
Date: 2 November 2007 6:05 PM
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Formation of ethanol: From fermentation. More recently industrial ethanol is made through the hydration of ethene from the petrochemical industry.
ACID CATALYST REACTION
CH2 = CH2(g) + H2O(g) acid H+→ CH3CH2OH (g)
Occurs at 300 degrees using sulfuric or phosphoric acid which is a catalyst.
DEHYDRATION
C2H5OH(g) concentrated H2SO4→ C2H4(g) + H2O(g)
Before catalytic cracking of petroleum fraction ethene was produced from ethanol. Industrially porous ceramic catalysts are used.
SOLUBILITY OF ETHANOL
In both hexane and water because it is non-polar (the hydrocarbon bit; an alkyl CH3 CH2-) and polar (OH bit). Dipole-dipole, H bonding and dispersion forces.
Title: 6 November 2007 Chemistry
Date: 6 November 2007 6:15 PM
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Ethanol as a fuel
Ethanol is renewable because it comes from things like sugar cane.
Fermentation of glucose:
C2H12O6 → 2C2H6OH + 2CO2
When burning ethanol the CO2 produced isn't adding to the Carbon in the world because the biomass is removing it at the same rate.
Combustion of ethanol (complete):
C2H5OH + 3O2 → 2CO2 + 3H2O + energy
energy = 1367 kJ/mol of ethanol
Title: 7 November 2007 Chemistry
Date: 7 November 2007 8:27 PM
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Conditions for fermentation:
-Yeasts require plenty of O2
-At the beginning of fermentation it must be aerated to build yeast population.
-As it ferments CO2 increases and anearobic conditions are attained. This means no mold/other crap.
-25-30°C
-pH should be a bit acidic
-Yeast grows in up to 40% sugar
Fermentation:
C6H12O6 (aq) → 2CH3CH2OH (aq) + CO2 (g) + heat
Title: 8 November 2007 Chemistry
Date: 8 November 2007 8:51 PM
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Oxidation/Reduction
Metals donate electrons to ions.
Reactive metals transfer electrons to other metal ions.
eg Zinc in CuSO4 gets coated in Cu.
Zn(s) + Cu2+(aq) → Zn2+(aq) + Cu(s)
Do your own half equations.
Title: 9 November 2007 Chemistry
Date: 9 November 2007 8:55 PM
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Rules for Oxidation States
- Substances in elemental state = zero eg C = 0
- Monatonic ions = their charge eg Cu2+ = 2
- Neutral molecules = zero eg H20
- Sum of oxidation states in a polyatomic ion is the charge eg SO42- = 6 + (4*-2) = -2
- Fixed oxidation states for:
- Group I = 1
- Group II = 2
- Combined oxygen = -2 (except peroxides (-1) and F2O (2))
- Combined Hydrogen = 1 (except metal hydrides (-1))
Title: 14 November 2007 Chemistry
Date: 14 November 2007 6:44 PM
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Galvanic Cells
Consists of two metal plates connected via wire. Each is immersed in an ionic solution. One plate (the one being oxidised) transfers electrons through the wire to the other plate (the one being reduced). This allows ions in the solution to join the electrons in the plate.The oxidised plate releases ions into the solution.
Allows a spontaneous redox reaction to occur. Electricity is produced.
Title: 20 November 2007 Chemistry
Date: 20 November 2007 6:01 PM
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A salt bridge is saturated with something like KNO3 Which allows flow of ions between the two containers. There are no reactions though. It just allows the charge to be balanced.
Anode: negative electrode (anode) where oxidation occurs therefore it is the more reactive metal.
Cathode: positive electrode where reduction occurs.
A voltmeter can measuer the voltage over the cell.
Title: 21 November 2007 Chemstry
Date: 21 November 2007 6:02 PM
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You can write the description of a galvanic cell like this:
Zn(s) | Zn2+(aq) || Cu2+(aq) | Cu(s)
This means solid Zn is going into Zn2+ solution. || represents a salt bride. Then Cu2+ is going into solid Cu.
| means change in phase.
An inert electrode is required when gas is bubbled through an electrolyte. Or if made of 2 ions.
eg.
C(s) | Fe3+(aq) Fe2+(aq) || Cu2+(aq) | Cu(s)
Pt(s) | Cl2(g) | Cl-(aq) ||
UPDATE WITH REDOX TABLES
Shipwrecks and Salvages (Option)
Title: 30 January 2008 Chemistry
Date: 30 January 2008 6:42 PM
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The ocean as an an electrolyte
The ocean is a giant electrolyte because it has salts in it (dissolved ones)
Hydrothermal vents at the mid ocean ridge put salts into the sea when the water enters hot rocks and is expelled.
Salt also gets into the sea from leaching: water moves through rocks, taking salts with it.
The ocean is a steady state system: salt is taken out as salt is brought in.
It is taken out by sea spray and marine animals eating the salt, also by mineral deposits.
Title: 30 January 2008 Chemistry
Date: 30 January 2008 6:44 PM
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Reactions of hydrocarbons with Bromine water
We added bromine water to some hydrocarbons. When the solution goes colourless, that means there were unsaturated hydrocarbons in that hydrocarbon.
Hexane - Colour
1-Hexene - Colourless
Cyclohexane - Colour
Toluene - Colourless
Apparently the Toluene result we got is wrong.
Title: 31 January 2008 Chemistry
Date: 31 January 2008 6:49 PM
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Oxidation: Loss of electrons
Reduction: Gain of electrons
OIL RIG
Oxidation is loss reduction is gain
Brushed up on galvanic cells, redox etc.
Title: 1 February 2008 Chemistry
Date: 1 February 2008 6:50 PM
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Corrosion:
When a metal reacts with oxygen and it is the natural deterioration of the metal.
If this happened on a building it would fall down. This is a bad thing
THE ACTIVITY SERIES OF METALS:
This can dictate how much it corrodes:
From least to most reactive:
Cu, Pb, Fe, Zn, Al, Mg
Passivating metals form a layer of non-pouros and inert stuff that stops further corrosion. eg Aluminium.
Metals like Iron form a layer but it is porous and doesn’t work.
Title: 5 February 2008 Chemistry
Date: 5 February 2008 2:57 PM
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Pig iron is from the blast furnace. It can be made into Cast iron. This can be made into either Wrote Iron or Steel.
Steel is iron and carbon and usually something else.
Pig iron is over 4% carbon and lots of other stuff. It sucks because its brittle.
Cast iron is 3% carbon and some silicon and magnesium. Hard and resilient so is used in anchors etc.
Wrought Iron has less of carbon etc. so it is more malleable.
Title: 6 February 2008 Chemistry
Date: 6 February 2008 2:46 PM
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The rusting of iron and steel.
Anodic Reaction:
Fe -> Fe2+ + 2e-
Cathodic Reaction
O2 + 2H2O + 4e- -> 4OH-
sOverall reaction
2Fe + o2 + 2H2O -. 2Fe2+ + 4OH-
Then the Ferrous ions are combined with Hydroxide
Fe2+ + 2OH- -> Fe(OH)2
Then it is hydrated.
4Fe(OH)2 + 3O2 + 4H2O -> 2(Fe2O3.H2O) + 2H2O
Water is an electrolyte when rusting. The more acidic the conditions the faster the rusting.
A less active metal will make the iron rust faster as a electrochemical cell is set up where iron is the anode.
Vice versa for more active metals.
Cracks and bends can increase rust. Oxidation occurs easily there.
If there is an impurity in the iron then rusting can occur easily as a cell is set up in the iron.
Title: 8 February 2008 Chemistry
Date: 8 February 2008 2:54 PM
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Revision of electrochemical cells.
Title: 11 February 2008 Chemistry
Date: 11 February 2008 5:16 PM
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IMPORTANT RULES
OIL RIG: Oxidation is Loss, Reduction is Gain
RED CAT: Reduction at Cathode
AN OX: Anode has Oxidation
Galvanic Cell: cathode is positive
Electrolytic cell: cathode is negative
To do the EMF fro galvanic:
Write out the half equations, the equation with the lower emf should have its sign reverse. Balance the equations and add the two emf’s
The one with the lower emf is the oxidation
The one with the higher emf is the reduction
If emf>0 it is spontaneous, a galvanic cell, Otherwise it needs external voltage.
IMPORTANT NOTE ABOUT ELECTROLYTIC CELLS
When considering the half equations, if the solution is aqueous then ALWAYS CONSIDER THE REACTION OF WATER. and at the anode ALWAYS CONSIDER THE REACTION OF THE ELECTRODE unless its inert.
The reaction that will occur is the one whose emf is closer to zero.
Title: 12 February 2008 Chemistry
Date: 12 February 2008 5:30 PM
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Electrolysis
In an electrolytic cell:
Sodium, potassium and magnesium ions are not reduced at the cathode because their potentials are too high. Water is reduced.
Sulfate and Nitrate arent oxidised at the anode water is.
Anodes may react is they are made of reactive metals.
Carbon electrodes don't react (yay)
If the solution is aqueous then consider water in the cell.
If an ion is very concentrated in solution it is probably the reactant.
Title: 14 February 2008 Chemistry
Date: 14 February 2008 5:42 PM
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Uses of electrolytic cells
Produce sodium hydroxide and chlorine gas
Refines metals
Plate objects
Clean corroded objects
Title: 15 February 2008 Chemistry
Date: 15 February 2008 5:44 PM
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ENTHALPY
This is important. I don’t think I will every get it right. Take this note as if it is wrong because it probably is. I find it very hard to understand how to calculate enthalpy.
∆H=-mC∆T
∆H Is the change in enthalpy, measured in J/mol
m is the mass of water in g
C is the calorimetre constant: 4.18 J/mol (maybe???)
∆T is the change in temp of the water
MAKE SURE YOU CONVERT kJ to J and kg to g
Title: 22 February 2008 Chemistry
Date: 22 February 2008 6:57 PM
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Ways the metal hull may be protected from corrosion:
Corrosion Resistant Metals
Steel can be covered in a metal that isn’t very reactive. This metal will form a passivating layer but if this layer is broken the hull is screwed. Iron can be galvanised. The zinc will turn into a anode.
Development of surface alloys
Bombarding mild steel with chromium and nickel ions as a plasma can forma a passivating layer on mild steel.
New Paints
Painting a hull keeps it from oxygen and water, preventing corrosion. However if the paint is scratched there will be corrosion. Enamel is a good paint because it is strong. Zinc paints become sacrificial anode when they are scratched which further protects the hull before the paint is corroded away. Some paints also form an inert coating.
Cathodic Protection
Get a more reactive metal than iron such as zinc. Bolt a block of it to the side of a ship. This zinc block will corrode INSTEAD of the iron. This is because a galvanic cell is set up. The zinc is the anode: it is oxidised: it loses electrons. Once the zinc is gone the iron will corrode. Works on the side of a ship but pollutes the water and needs to be replaced alot.
You could also hook up a circuit to the iron. Pass a current through from a battery to the iron. On the other terminal (the positive one) of the battery is an inert electrode (it should be in the water with the hull but not really touching it). The electrons a forced from the electrode to the iron instead of the other way around like usual. This is an impressed current. Good for underground piping where you cant replace a zinc block. No pollution.
Title: 25 February 2008 Chemistry
Date: 25 February 2008 4:56 PM
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If 2 metals are in contact the one with the lowest electrode potential/emf is corroded. It oxidises more easily. It turns into a cation.
Title: 26 February 2008 Chemistry
Date: 26 February 2008 5:45 PM
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If you bend a nail hen the lattice of the metal is weakened and it becomes a site for rusting and oxidation.
Title: 27 February 2008 Chemistry
Date: 27 February 2008 2:25 PM
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The effect of temperature on gas solubility: The colder, the more soluble gas is in water.
The effect of pressure on gas solubility: The more pressure the more soluble the gas is.
The effect of temperature on salt solubility: The colder, the less soluble a salt is.
The effect of pressure on salt solubility: There is no effect of pressure on salts.
Gases dissolved in oceans: LOTS of CO2 as it reacts with the water to form carbonic acid.Not too much oxygen at low depths as it is used up by bacteria before it gets there. At the surface there is more oxygen than in the atmosphere.
AT great depths, there is corrosion even though there isn’t much oxygen in the water. According to the information at the top, as we go down in the ocean there should be heaps of oxygen. There isn’t.
We did a prac on fermenting sugar to alcohol. It failed miserably.
Title: 28 February 2008 Chemistry
Date: 28 February 2008 2:41 PM
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Temperature decreases with depth, pressure increases with depth.
If a big iron thing is poking out of the water, it will rust a lot because it is in contact with an electrolyte (the sea), oxygen and water.
Title: 4 March 2008 Chemistry
Date: 4 March 2008 6:50 PM
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Why does corrosion happen at low depth? It is because of sulfate-reducing bacteria. On the Titanic there was a lot of black metallic sulfides such as FeS.
The environment down at a shipwreck is very acidic. This is caused by the huge amounts of Carbon Dioxide. It forms carbonic acid with the water. Organic materials such as dead things and wood also make the water acidic. Hydrogen ions are produced when metallic sulfides precipitate.
The hydrogen ions are good oxidising agents as they oxidise iron and are reduced themselves. Oxygen also is a good oxidant. Even though there isn’t much there, it helps.
An anaerobic bacteria is one that doesn’t require oxygen.
Anaerobic bacteria reduce sulfate ions to sulfur then sulfur ions.
Iron from the wreck provides the electrons for the bacteria to reduce the sulfate.
Rusticles formed because it was really acidic. Iron is oxidised and hydrogen ions are reduced. The Iron ions react with water to form Iron hydroxide.
Title: 7 March 2008 Chemistry
Date: 7 March 2008 2:34 PM
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Anaerobic bacteria at depths cause corrosion. They use sulfate ions and reduce them to Sulfur. Then reduced again to S2-
Iron is oxidised to produce the electrons for this reduction.
Metal sulfides for which are black.
The bacteria are called Sulfate Reducing Bacteria (SRB)
Hydrogen Sulfide is formed too.
Title: 11 March 2008 Chemistry
Date: 11 March 2008 8:23 PM
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Restoring Artifacts
Wood and Leather: soaked in fresh water so salts can diffuse out into it. The water is replaced several times until it is mostly out.
Iron: Soaked in sodium hydroxide solution then becomes the cathode in an electrolytic cell. Treated with wax. Heated to remove water.
Copper: Corrosion is stripped with citric acid. Electrolytic cell reduction. Lacquered.
Silver: Soaked in acid to remove concretions then electrolytically cleaned.
Lead: Electrolysis, lacquered
Removing Concretions: Removed by physical of chemical force.
The Acidic Environment
Title: 12 March 2008 Chemistry
Date: 12 March 2008 12:32 PM
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Properties of Acids:
Conducts electricity
Tastes sour
Turns blue litmus red
acid + reactive metal → hydrogen gas + salt
acid + carbonate → water + salt + carbon dioxide
acid + metal oxide → salt + water
acid + metal hydroxide → salt + water
Properties of bases:
Red litmus → blue
Bitter
Conducts electricity
acid + base → salt + water
PRAC
Factors that can affect the rate of electrolysis.
You have a beaker set up with two copper electrodes in an electrolysis setup.
The experiment variables are, using 2V, 4V, 6V
Using 5cm wide electrodes instead of 2 in the other variables
5cm apart electrodes instead of 2cm apart in other variables
Lower molarity solution.
Results were inconclusive.
Title: 25 March 2008 Chemistry
Date: 25 March 2008 6:54 PM
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Elements to the right of the periodic table (excluding nobel gases) tend to form nonmetal oxides which are acidic oxides.
Elements to the left tend to make metal oxides which are basic.
Some of the elements form amphoteric oxides which display properties of both bases and acids.
Nonmetal oxide + water -> acid
Acidic oxide + base -> water + salt
Metal oxide + water -> base
Basic oxide + acid -> water + salt
The atmosphere contains nonmetal oxides. These are produced naturally (eg Volcanoes) and through human causes (eg Industrial Revolution)
There is Carbon Dioxide (created through respiration, used by photosynthesis, created by combustion)
There is Sulfur Dioxide/Trioxide (killed 4000 people during the Industrial Revolution and it causes acid rain when dissolved in water) (comes from volcanoes too)
Title: 26 March 2008 Chemistry
Date: 26 March 2008 9:09 PM
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When the Industrial Revolution rolled around, 4000 old people died because of sulfur dioxide pollution. There was sulfuric acid in the smog that came.
It comes naturally from decomposition/combustion of organic matter and also from volcanoes.
It comes from fossil fuel burning in the industry. Also Metal smelting.
Sulfur and oxygen in the atmosphere form sulfur dioxide. It dissolves in water to form sulfurous acid (?)
Nitrogen Oxides also come from fossil fuels and organic stuffs.
There is NO2 (Nitrogen Dioxide), N2O (Dinitrogen monoxide), NO (Nitrogen monoxide)
Prac:
Boil cabbage. Decant the liquid. Put the liquid in stuff. Note the colour change.
You has just made an indicator of pH
Nuther Prac:
From the corrosion option topic:
Put a nail in different conditions. You will find that:
The more oxygenated the water, the more rust will occur.
The more warmth in the environment, the more rust will form.
The more salt in the solution, the more rust will occur.
The lower the pH of the solution, the more rust will form.
But of course you knew that already.
Title: 29 April 2008 Chemistry
Date: 29 April 2008 7:44 PM
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Le Chatelier’s Principal
A system is at equilibrium. If this equilibrium is disturbed then the system will change to compensate. A disturbance can be caused by a change in pressure of one of the gasses involved or a change in concentration of one of the other substances. Also a change in temperature.
CO2 + H2O <-> H2CO3 + heat
This is carbon dioxide and water turning into carbonic acid and back.
If the pressure of the CO2 is increased then it will dissolve more, ‘pushing’ the reaction to the right
If an acid is added to the solution, the equation is pushed to the left as more carbonic acid is present.
A decrease in CO2 pressure means the equation is pushed to the left; making more CO2
If the pressure on the system increases, the equation is pushed to the right to reduce the total pressure. More CO2 dissolves and removes pressure.
The reaction is exothermic so if the system is heated then it will be pushed to the left to get absorb the heat
Catalysts increase the RATE of reaction ONLY.
Title: 30 April 2008 Chemistry
Date: 30 April 2008 8:32 PM
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Did you know if chickens get hot, they pant more and their egg shell’s get weaker?
Title: 2 May 2008 Chemistry
Date: 2 May 2008 8:32 PM
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Acid rain has a pH of 5.6 or less.
Dry deposition is when sulfur and nitrogen oxides deposit on surfaces then get wet and acidify.
Acid rain comes from volcanoes, lightning, and smelters, power stations and industrial furnaces.
It dissolves metals which run into streams, killing things.
Title: 13 May 2008 Chemistry
Date: 13 May 2008 9:09 PM
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Acid: proton donor
Base: proton acceptor
A hydronium ion is H3O+
Formed when hydrogen ion attaches to water. pH stands for potential Hydrogen. each number from 1 - 14 represents a drop or increase by a factor of 10.
To work out pH:
pH = -log10[H+]
The product of hydrogen ions and hydroxide ions is always the same at a given temperature. At 25 degrees C it is 10^-14
Title: 14 May 2008 Chemistry
Date: 14 May 2008 6:45 PM
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Release of oxides of sulfur and nitrogen into the environment:
Unclean energy is cheaper for the consumer. The switch to clean sources would cost a lot of money and need changes to infrastructure. It causes respiratory disorders and death, photochemical smog and the greenhouse effect. Kills animals and plants.
Then we weighed and opened some tonic water, let the gas escape, warmed it up and agitated it and then weighed it again. The tonic water lost mass.
Title: 15 May 2008 Chemistry
Date: 15 May 2008 1:58 PM
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[H+][OH-]= 1.0 x 10-7 mol L-1
pH = -log10[H+]
Title: 21 May 2008 Chemistry
Date: 21 May 2008 10:52 PM
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Strong acid has its atoms dissociate into ions in water completely.
Weak acid only dissociates a bit.
Concentrated means there is a lot of mols per litre.
Dilute means there are less.
Title: 23 May 2008 Chemistry
Date: 23 May 2008 12:56 PM
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To calculate the pH of a solution:
-log10[H+]
H+ is the concentration of H+ ions in mols per litre.
Title: 28 May 2008 Chemistry
Date: 28 May 2008 12:57 PM
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Acetic Acid: CH3COOH (Vinegar)
Citric Acid: C6H8O7
Ascorbic Acid: C6H8O6 (
Sodium Carbonate: Na2CO3 (Glass, Paper)
Sodium Bicarbonate: Na2HCO3 (Indigestion treatment)
Ammonia: NH3 (Polymers, Explosives, Fertiliser)
Titration: The process of measuring the amount of standard solution needed to neutralise the unknown.
Measures the molarity of an unknown substance by neutralising it with a known substance.
Primary Standard: Solution created from a known pure solid acid/base
Secondary Standard: Molarity known through titration against a primary standard.
Strong acid weak base: methyl orange
Strong acid strong base: bromothymol blue
Weak acid strong base: Phenolphtalene
Title: 30 May 2008 Chemistry
Date: 30 May 2008 1:04 PM
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Food Preservation:
Acids are used in food to preserve them. They kill bacteria. They can also add flavour.
Title: 3 June 2008 Chemistry
Date: 3 June 2008 1:06 PM
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Lavoisier: Predicted in 1780 that acids all contain oxygen. When oxides dissolve in water they make acids.
Davy: Predicted in 1810 that HCl didn’t have oxygen in it and that acids all have hydrogen in them.
Arrhenius: predicted in 1884 that acids have hydrogen ions in solution
Bronsted-Lowry:
An acid base reaction involves the transfer of a proton between species. Acids donate, bases accept.
Conjugate acid/base:
e.g. CH3COOH + OH- -> H2O + CH3COO-
Acid + Base -> Conjugate acid + conjugate base
Title: 4 June 2008 Chemistry
Date: 4 June 2008 1:15 PM
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Amphiprotic substances can act as acids or bases (proton donors or acceptors)
e.g. HCO3-
When reacting with water HCO3- can go either way.
Title: 6 June 2008 Chemistry
Date: 6 June 2008 1:19 PM
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n=CV
where n = number of mols
C is concentration in mols per litre
V is volume of solvent
In a titration:
Strong acid strong base: equivalence at pH=7, use bromothymol blue
Strong acid weak base: equivalence at pH<7, use methyl orange
Weak acid strong base: equivalence at pH>7, use Phenolphtalein
To make a primary standard:
must be in pure form (no HCL or H2SO4)
must have known chemical formula
does not react with air (No NaOH)
soluble
Usually Na2CO3 is used for base or H2C2O4.2H2O for acid
Title: 11 June 2008 Chemistry
Date: 11 June 2008 8:37 PM
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ACID BASE TITRATIONS
A standard solution is used. You get a set amount of an acid or base and dilute it. Rinse burette with water then with the solution. Fill it with the solution.
Weigh conical flasks with at least three samples of a made up known primary standard. Add indicator appropriate to this titration. When the indicator is about to change, stop, swirl.
If you think the solution has completely changed, wait. Swirl it around a bit. Once after 30 seconds of swirling one of our solutions changed colour twice.
Title: 12 June 2008 Chemistry
Date: 12 June 2008 8:42 PM
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ESTERS have similar structure to alkanoic acids. Although they have an alkyl group instead of a hydrogen group attached to the oxygen.
RCOOR (where R is an alkyl group)
For example: Methyl ethanoate is CH3COOCH3
Ethyl butanoate is: CH3CH2CH2COOCH2CH3
The first part of the name is the alkyl group and the next bit is the acid bit (the other bit on the other side of the COO)
The carboxylic acids have higher boiling points than other acids because they have two oxygens available to hydrogen bond with.
Chemical Monitoring and Management
Title: 25 June 2008 Chemistry
Date: 25 June 2008 12:36 PM
Category: School
Tags:
THIS IS A NEW TOPIC BUT I DON’T KNOW WHAT IT IS CALLED YET
Describe an example of a chemical reaction such as combustion where reactants form different products under different conditions and thus would need monitoring
Methane or propane:
Heat of the flame depends on how open the hole in the bunsen is.
If fully open, methane and oxygen form carbon dioxide and 2 waters
Propane and oxygen forms carbon dioxides and waters
If half open, methane and oxygen forms carbon monoxide and waters
Propane forms carbon monoxides and waters
If the hole is not open, methane forms carbon and waters
Propane forms carbons and waters.
The product of the reactions depend on the amount of oxygen. Try writing the above equations. You will need to used different amounts of oxygen as a reactant.
Oh wait, its called Chemical Monitoring and Management.
Title: 29 July 2008 Chemistry
Date: 29 July 2008 11:39 AM
Category: School
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Analysis of Ions
Here are some ways to check for ions in a substance.
Fe3+ : Add Hydroxide and you will get a brown precipitate of ironIII hydroxide
Cu+ or Cu2+ : Flame test and you will get blue green flame or add hydroxide and get deep blue precipitate. (dissolves in hydroxide excess)
Fe2+ : Add hydroxide and get white ironII hydroxide which oxidises to redbrown ironIII hydroxide
Pb2+ : Add iodide and get yellow lead iodide (PbI2)
Ba2+ : Flame test to get green flame or add sulfate to get white barium sulfate
Ca2+ : Flame test to get orange or red flame or add carbonate and get white calcium carbonate
Cl- : Add silver nitrate and get white silver chloride
CO32- : Add dilute hydrochloric acid and get CO2 gas which turns limewater (Ca(OH)2) milky. Most CO32- substances are insoluble except group one.
SO42- : Add barium ions to get white barium sulfate (insoluble in HCl). Barium carbonate is also insoluble and white.
PO43- : Add silver nitrate and get yellow cloudiness in your solution
Title: 4 August 2008 Chemistry
Date: 4 August 2008 10:10 PM
Category: School
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Atomic Absorption Spectroscopy
A technique pioneered by Alan Walsh at the CSIRO in 1952.
It is to find the concentration of an element in a substance by the absorption spectrum of that element.
You suck up (aspirate) into flame and then shine a light through it. The frequency of the light depends on the element you are finding the concentration of. A detector on the other side detects the original light and the light emitted from the element to find it’s concentration accurately.
Title: 7 August 2008 Chemistry
Date: 7 August 2008 12:56 PM
Category: School
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Prac:
Spray Ions into a flame to watch it change colour flame.
Add ions together to see the colour of the precipitate.
Title: 8 August 2008 Chemistry
Date: 8 August 2008 12:45 PM
Category: School
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Oxygen, Ozone and The oxygen free radical
Oxygen: colourless, odourless. Formed through photosynthesis. It is diatomic
Ozone: pale blue and toxic, smelly. Formed when UV bonds oxygen gas and a free radical. One single bond and one double bond. Bent
Oxygen free radical is formed when UV busts up an ozone molecule. Highly reactive.
Title: 12 August 2008 Chemistry
Date: 12 August 2008 10:20 PM
Category: School
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CFC’s. Chlorofluorocarbons, Haloalkanes and haloalkenes.
Haloalkanes are alkanes with a halogen(s) in them (group VII element)
They are inert and don’t react with stuff. OR SO WE THOUGHT.
When they get into the atmosphere, they are broken up by UV light. So there is a free radical halogen floating about. What else would it do but bust up some ozone and bond with an oxygen. An oxygen free radical busts up this bond and the halogen is now free to bust up some more ozone, thus depleting the ozone layer.
The Montreal Protocal is an international agreement to stop the use of CFC’s. Unfortunately they stay in the atmosphere for a very long time.
Title: 13 August 2008 Chemistry
Date: 13 August 2008 9:23 PM
Category: School
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Ozone is at its most plentiful in the stratosphere and harmful in the troposphere. It blocks UV light from reaching earth and causing damage such as immune system suppression and cancer as well as plant damage. A spectrometer measures ozone in the atmosphere, preferably from a satellite.