Khamis, 24 September 2009
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Uses of sulphuric acid
•Manufacture of fertilisers such as ammonium sulphate.
•Manufacture of electrolyte in lead-acid accumulators.
•Manufacture of soaps and detergents.
•Manufacture of pesticides (insecticide).
•Manufacture of plastic items such as rayon and nylon.
•Manufacture of paints.
Manufacture of sulphuric acid in industry
•Sulphuric acid is manufactured in industry through the Contact process.
Manufacture of ammonia and its salt.
Uses of ammonia
•Manufacture of nitrogenous fertilisers such as ammonium phosphate.
•Manufacture of nitric acid through the Ostwald process.
•Manufacture of electrolytes in dry cells.
•Manufacture of cleaning agents such as washing powder and detergents.
•Manufacture of explosives such as trinitrotoluene (TNT).
•Manufacture of dye.
Properties of ammonia
•Very soluble in water.
•Less dense than air.
•Produces thick white fumes with hydrogen chloride, HCl, gas.
•Has characteristic of weak alkali when dissolve in water.
Manufacture of ammonia.
1.Ammonia is manufactured on a large scale in factories through the Haber process.
2.In the Haber process, nitrogen and hydrogen gases are mixed in the ratio of 1:3 volumes (or moles).
3.The hydrogen gas is obtained from methane, a type of natural gas, while nitrogen gas is obtained from air by fractional distillation of liquified air.
4.The gas mixture is passed over iron (catalyst) at a temperature of 450-550 C
5.The ammonia gas obtained is cooled (temperature of -50 C) to become liquid ammonia.
•An alloy is a compound formed from a mixture of metal and other elements.
•An impurity atom (foreign atom) may be atoms of other metals or non-metals such as carbon.
•The process of mixing atom of impurities with atom of pure metal by melting is called alloying.
•The aim of alloying are to:
@ increase the strength and hardness of the metal.
@ prevent corrosion of the metal.
@ improve the appearance of the metal so that it is more attractive.
Synthetic Polymers and Their Uses
•Long chains of molecules made from combinations of many small molecule.
•Small molecule that combine to form polymers are called monomers.
•Can be divided into two types:
@ natural polymer
@ synthetic polymer.
•A process of combining monomers to form a long chain of molecules.
The uses of glass and ceramics
•Brittle @ hard
•Chemically inert @ transparent
•Heat insulator @ not permeable to gas and liquid (fluid)
•Does not conduct electricity.
Fused silica glass
•Lenses, spectacles, laboratory glassware, ultraviolet column.
•Glass, bottle containers, mirrors, electrical bulbs, glass windows.
•Bowls, plates, pots, cookware, automobile headlights and laboratory glassware.
Lead crystal glass
•Lenses, prisms, glasses, ornamental items (crystals).
•A compound produced when the hydrogen ion from an acid is replaced by a metal ion or an ammonium ion.
•Consist of cations (positive ion) originating from bases that combine with the anions (negative ions) originating from acids.
•The reaction between an acid and a base produces salt.
Uses of salts
•Ammonium phosphate is used as fertiliser.
•Copper (ll) sulphate and iron (ll) sulphate are used as pesticides to kill pests.
•Silver bromide is used to make film and photography paper.
•Calcium sulphate is used as plaster to support broken bones
•Potassium manganate(Vll) is used as antiseptic on wounds.
•Barium sulphate is taken by patients going for X-rays.
•Sodium bicarbonate (sodium hydrogen carbonate) is used to raise dough for bread and cakes.
•Monosodium glutamate (MSG) is used for food flavouring.
•Sodium chloride, NaCl, and sodium nitrite is used te preserve food such as fish and prawns.
•Chilli sauce and tomato sauce contain sodium benzoate as preservative.
• A chemical compound which dissociates (ionises) to produce hydrogen ion (or
hydroxonium ion), when dissolve in water.
• Example of acids
@ hydrochloric acid
@ nitric acid
•Acid is a proton donor.
@one molecule of an acid dissociates in water to produce one hydrogen ion.
@ one molecule of acid dissociates in water to produce two hydrogen ions.
Properties of an acid
•Taste sour @ Is corrosive
•Turns blue litmus paper red @ Has a pH value below than 7
•Reacts with reactive metal such as Magnesium, Mg, aluminium, Al, zinc, Zn, iron, Fe, to release hydrogen gas.
•React with carbonate such as calcium carbonate to release carbon dioxide.
•Reacts with a base to form salt and water.
•Neutralises an alkaline solution to form salt and water only.
•A chemical compound that can react with acid to form salt and water.
@ sodium oxide @ sodium hydroxide crystals
@ potassium hydroxide solution @ sodium hydroxide solution
@ calcium hydroxide solution @ ammonia solution
•Not all bases can dissolve in water. A base that dissolves in water is called an alkali.
•A base that is not dissolve in water will remain as a base.
Application of acids and alkalis in daily life
•Carbonic acid is used to manufacture soft drinks.
•Vinegar contains ethanoic acid and can be used as food preservatives.
•Sulphuric acid is used as an electrolyte in car batteries.
•Methanoic acid solidifies latex.
•Hydrochloric acid is used to remove rust
•Yoghurt contains lactic acid.
Examples of applications of alkalis in daily life.
•Soaps and detergents contain sodium hydroxide.
•Toothpaste contains magnesium hydroxide (weak alkali).
•Gastric pills contain aluminium hydroxide or magnesium hydroxide (weak alkali).
•Ammonia solution is used to make chemical fertilisers and prevent solidification of latex.
•Calcium hydroxide is used to make cement.
Properties of alkali
•Taste bitter and feels smooth @ Is corrosive
•Turns red litmus paper blue @ Has a pH value of above 7
•Reacts with ammonium salt such as ammonium chloride to produce salt, water and ammonia gas when heated.
•Neutralise an acidic solution to form salt and water.
Concentration of Acid and Alkali
Concentration of the solution
•The measurement which show the quantity of the dissolved solute in 1dm^3
of the solution.
•Unit : g dm^-3 / mol dm^-3
•Formula ( g dm^- 3) :
= mass of solute (g) / volume of solution (dm^3)
•Formula ( mol dm^-3)
= number of mole of solute (mol) / volume of solution (dm^-3)
•Concentration of a solution measured in mol dm^-3.
•The unit of the concentration that shows the number of moles of a solute that dissolves in 1 dm^3 of solution.
molarity = number of moles of solute / volume of solution in dm^3
Relationship between number of moles with molarity and volume of solution.
MV / 1000 = number of moles
Where M = Molarity of solution ( mol dm^-3)
V = Volume of solution (cm^3)
•A chemical compound which conducts electric current in a molten state or aqueous solution and undergoes chemical change.
•Contain ion which more about freely to carry electrical charge.
•Can break down into its elements at electrods when an electric current flows through it.
•A chemical compound which cannot conduct electric current in all states.
•No charge on a non-electrolyte when an electric current flows through it.
•Made up from molecules only. There are no ions which can carry electrical charges in non-electrolyte.
Electrolysis Of Molten Compound
•The process of breaking down chemical compounds into their constituent elements using electric current.
•An electrolyte in the form of molten compounds or aqueous solution can be broken down into its element.
•A type of cell which uses electrical energy to produce chemical reaction.
•Reaction in electrolytic cell will not occur without an external source of electrical energy.
•Anode (connected to the positive terminal of an electric source).
•Cathode (the electrode which is connected to the negative terminal of an electric source).
Cation and anion in molten compounds
•A molten compound which can be electrolysed is made up of ionic compounds.
•Cation (positively charged ion)
•Anion (negatively charged ion)
•In solid state
@ cations and anions in ionic compounds are not free to move. This is
because cations and anions are arrange in a fixed crystal lattice.
@ there are no free ions to move and carry electrical charges, solid ionic
compound cannot conduct electricity.
•In molten form
@ cation and anion in ionic compounds move freely to carry electrical
charges. Thus, molten ionic compounds can conduct electricity.
Electrolysis of molten compound
@ anions (negative ions) will be pulled towards the anode (positive
electrode). At the anode, cations will be discharged by accepting
electron from the cathode.
@ Cations (positive ions) will be pulled towards the cathode (negative
electrode). At the cathode, cations will be discharged by accepting
electrons from the cathode.
Electrolysis Of Aqueous Solution
Cation and anions in aqueous solutions
•Water molecules in a aqueous solution slightly dissociate to produce hydrogen ions and hydroxide ions
•Thus, aqueous solution contain hydrogen ions and hydroxide ions besides electrolyte ions.
•When there is more than one type of cation attracted to the cathode or more than one type of anion attracted to the anode, the choice of ion to be discharged depends of the following factors:
@ position of the ions in the electrochemical series ( ECS ).
@ concentration of ions in the electrolyte.
@ type of electrode.
Concentration of ions in electrolyte solutions
•Concentration of ions in electrolyte solution, also affects the choice of ions to be discharged.
•An ion that is more concentrated is preferable discharged.
•However, the concentration of ions normally affect the choice of ions to be discharged at the anode only.
•The type of ion chosen for discharged at the cathode is still determined by the position of ion in the ECS.
ELECTROLYSIS IN INDUSTRIES
Extraction Of Metal
•Electrolysis can be used to extract metals from their ores.
•Metals that are more reactive than carbon such as:
@ potassium @ magnesium
@ sodium @ aluminium
cannot be extracted through heating of their metal oxides with carbon.
•Metal that are more reactive need to be extracted from their molten ores using the electrolysis process.
•In the process, the molten ore is the electrolyte and inert electrodes such as carbon are used as positive and negative electrodes.
Purification Of Metal
•Metal that have been extracted from their ores are normally not pure and contain impurities which need to be removed.
•These metal can be purify by electrolysis.
•In the purification process, the impure metal is made the anode while the pure metal plate is made the cathode.
•The electrolyte is the solution which contain the metal ions.
•During electrolysis, impure metal at the anode will release electrons and dissolve into the electrolyte as metal ions.
•These metal ions can receive electrons and form pure metal at the cathode.
•The size of impure metal (the anode) becomes smaller and impurities will settle at the bottom of the container.
•The size of pure metal (the cathode) becomes larger due to the deposition of pure metal. The mass of pure metal plate increase.
Electroplating Of Metals
@ metals that can be plated with other metals through electrolysis.
•The aim of metal plating through electrolysis includes:
@ making the metal more resistant to corrosion.
@ making the metal appear more attractive.
•Metal that frequently used as plating metal:
@ silver, Ag @ cadmium, Cd
@ gold, Au @ copper, Cu
@ nickel, Ni @ zinc, Zn
@ chromium, Cr @ tin, Sn
@ plating metal is used as the anode while metal to be plated is used as a
•The electrolyte used
@ an aqueous solution which contains ions of the plating metal.
@ plating metal or the anode releases electrons and dissolves to form metal
@ ions of the plating metal then, move to the cathode, receive electrons there
and form a thin layer of metal on the cathode.
•A type of cell which produces electrical energy from the chemical reactions occuring inside it.
•Chemical energy is transformed into electrical energy.
•Example of chemical cell
@ simple voltaic cell @ Daniell cell
@ lead-acid accumulator @ dry cell
@ alkaline cell
Simple voltaic cell
A simple voltaic cell
•Has 2 different conductors (metal or carbon) which are immersed in an electrolyte solution and connected to each other with connecting wires.
•The conductors are connected through and external circuit to a bulb, ammeter, voltmeter or galvanometer.
•Metal that located higher up in the ECS (more electropositive metal) will get at the negative terminal and vice versa.
•At the negative terminal, the metal electrode will release electron and dissolve to form metal ions.
•At the positive terminal, cation of a metal will accepts electrons and be discharged to form neutral atoms.
@ made up of two electrodes of different type of metals that immersed in two
separate electrolyte solutions.
@ the electrolyte solution in Daniell cell can be separated either by a porous
pot or salt bridge.
•Porous pot / salt bridge
@ function : to separate two electrolyte solutions but allows ion to pass
through in to complete circuit.
@ can be made from any electrolyte that does not react with the electrodes in
the Daniell cell.
@ example : dilute sulphuric acid
: sodium nitrate solution
: potassium chloride solution
@ basically same as a simple voltaic cell.
@ produce electrical energy.
@ metals that are located at higher position in ECS act as the negative
@ metals that are located at lower position in ECS act as the positive terminal.