Note If the oxidation numbers of all elements remain unchanged, the reaction is not a redox reaction. This is the oxidising agent. This is the reducing agent. Y is the oxidising agent. X is the reducing agent. Remember Oil RIG. The oxygen atoms caused this loss by taking away the electrons. Oxygen 0, is the oxidising agent. The calcium atoms caused this gain by donating the electrons.
Calcium Ca is the reducing agent. Hydrogen sulfide has been oxidised. Chlorine is the reactant that caused this increase in oxidation number. Chlorine CI, is the oxidising agent. Chlorhne has been reduced. Hydrogen sulfide is the reactant that caused this decrease in oxidation number. Hydrogen sulfide H,S is the reducing agent. Co mmon oxidising and reducing agents Some su bstances always behave as oxidising agents and others always behave as reducing agents.
A visible change may occu r when some of these react. Table Dilute or concentrated nitric acid, A brown gas is evo lved. Potassium iodide solution, Kl aq Colourless to brown. Iodine I , forms which di sso lves forming a brown solution. Aqueous iron lI salts, Fe" aq Pale green to yellow-brown. The pale green Fe" ion forms the yellow-brown Fe" ion. Hydrogen sulfide gas, H,S g A yellow precipitate forms. Solid sulfur 5 forms. Concentrated hydrochloric acid, A yellow-green gas is Chlorine gas CI, is produced.
HCI aq evolved. Substances that can behave as both oxidising and reducing agents So me com pound s can act as both oxidising a nd redu ci ng agents. Their be haviou r depends on the o th e r reactant. Acidified hydrogen peroxide, H I H20 2 Acidified hydroge n pe roxide is usually an oxidising agent. The acidified hydroge n peroxide reduces th e purple Mn0 4 - ion to the co lou rless Mn" ion; and the orange C r, O ,'- io n to the green Cr" ion, respectively. Sulfur dioxide, SO Sulfur dioxide is usually a reducing agent.
Tests for oxidising and reducing agents Ce rtain tests can be performed in th e laboratory to determine if an unknown substance is an oxidising or red uci ng age nt. Tests for the presence of an oxidising agent To test to see if a substance is an oxidising agent, add it to a known reducing agent, which gives a visib le change whe n oxidised. The reducing agents usually used are potassium iodide solution or a n aqueou s solution of an iron lI salt. Tests for the presence of a reducing agent To test to see if a substa nce is a reducing agent, add it to a kno wn oxidising agent, which gives a visible change when it is reduced.
The oxidising agents usually used are acidified potassium manganate VII so lution or acidified potassium dichromate VI solution. Browning of When some fruits and vegetables are peeled or cut, e. Preserving Sodium sulfite Na, 50, and sulfur dioxide SO, are reducing agents used as food food preservatives, e. They prevent spoilage of foods by I'reventing oxidation, e. They also prevent browning by reducing any melanins back to their colourless form.
For EACH reagent, give the colour change you would expect and explain this colour change. These are reactions that either produce electrica l energy or require electrical energy to proceed. Predicting reactions using the electrochemical series of metals The electrochemical series of metals places meta ls in o rd er of how easi ly they lose electrons ionise ' and can be used to predict certain chemical reactions.
The ability of metal atoms give away donate el ect rons to another reactant increases going up the se ries. Th erefore, the strength as a reducing agent increases going up the series. The higher metal is a stronger reducing agent, so it readily gives electrons to the ions of the lower meta l.
In doing so, the higher metal ionises to form ca tion s. The ions of the lower metal gain these electrons and are discharged to form atoms. The zinc atoms ionise and form Zn " ions. Metals below hydrogen do not react with acids because they do not di splace the H' ions. Th e magn es ium atoms ionise and fo rm Mg" ions. H, g Predicting reactions using the electrochemical series of non-metals Th e electrochemical series of non-metals places non-m eta ls in order of how eas ily th ey gain electrons, ionise , and ca n be used to predict ce rtain chemi ca l reactions.
The ability of non-metal atoms to io ni se and take away electrons from another reacta nt increases going up th e se ri es.
Therefore, th e strength as an oxidising agent inc rea ses go ing up the se ries. Th e higher non-m etal is a stronger oxidising agent, so it readil y takes electro ns fro m the io ns of the lower non-metal. In doi ng so, th e hi gher non-metal ionises to form ani o n s. The ion s of the lowe r non-metal lose these electrons and are discharged to form atoms. The chl orin e atom s ionise and form CI - ions.
Metals, graphite, molten ionic compoun ds, aqueo us so lutions of ionic compounds, ac id s and alkali s are conductors. Non-m etals except graphite , plastics, so lid ion ic compounds, cova lent com pou nd s and aqueous solution s of cova lent co mpou nd s are non-conductors.
Because the ionic bonds have broken and the ions are free to move, electrolytes are conductors. When an electric cu rrent passes through an electrolyte it decomposes. Difte rences between metallic and electrolytic conduction Di ffere nces ex ist between conduction in a metal metallic cond uction and conduction in an electro lyte electrolytic conduction. The metal remains unchanged chemically. The electrolyte decomposes, i. Their solu tion s contai n a high co ncentration of io ns. Examples includ e aqueo us soluti ons of ionic compounds, strong acids and strong alkali s.
Their so lutions co ntain a low concentratio n of ion s. Examples include w ea k ac id s and weak alkali s. ApprOXimately one in every 5. N on-electrolytes Non-electrolytes are substances which remain as mo lec ules in the liquid state or di sso lved in water, an d therefore they do not contain any ion s.
So luti ons of cova lent substance s, e. This is a molten ionic compound or solution which contains mobile ions. Thi s supplies the electric current. These are connected to the power supply by wires and are placed in the electrol yte so that they can carry the current into and out of th e electrolyte.
Th ey are usually made of an inert material, e. Th e anode behaves as the oxidising agent. The electrons re- enter th e circuit from the negative term inal of th e battery and move from the battery to th e ca thod e.
Th e cathode behaves as the reducing agent. Both ions are discharged during electrolysis. Bromine atoms immediately bond covalently in pairs to form bromine molecules: 2Br- I - -. During electrolysis, one type of cation and one typ e of anion are discharged in preference to any others prese nt. This is called preferential discharge. If an active anode is used, the reaction occurring is the one which requires the least energy.
This usually involves the anode ionising instead of an anion being discharged. Comparing the electrolysis of copper ll sulfate solution using an inert anode and an active copper anode demonstrates this see Table This rule applies mainly to solutions containing halide ions CI-, Br- and 1- ions.
Comparing the electrolysis of dilute and concentrated sodium chloride solutions using inert electrodes demonstrates this see Table Ions at the top of series are the hardest to discharge because they are the most stable.
Ions at the bottom are the easiest to discharge because they are the least stable. The ion which is lower in the electrochemical NO series is discharged Figure l1. Th e lower the ion in th e electrochemical series of cations, the more likely it is to be preferentially di scha rged.
Ions at the top of the series are the hardest to discharge because they are th e most stable. Ions at th e bottom are the easiest to discharge because they are th e [ea st stable. Effervescence occu rs as hydrogen gas is evolved. Pink coppe r is deposited and th e cathod e increases in size. Revision questions 1 Predict w heth er a displacement reaction w ill occur w hen EACH of the following are mixed and write a balanced eq uatio n for EACH reacti o n that yo u predict will occur.
Quantitative electrolysis During electrolysis, the movem ent of electrons thro ugh the external circ uit from anode to cathode results in a flow of electrical charge since each elect ron possesses an ext reme ly sma ll electrica l charge. The quantity of a su bstan ce produced at, or dissolved from, an electrode during electrolysis is directly proportional to the quantity of electrical charge, o r quantity of electricity, w hich flows through the electrolytic ce ll.
The quantity of electrica l charge Q , is measured in coulombs C. Current is measured in amperes k nown as amps, A. Time is measured in seconds 5. The quantity of electri ca l charge can be ca lculated using th e formula below.
Thi s val ue is known as the Faraday constant. The Faraday con, ,lllt i! M 1 mol or N- l The Faraday constant can be used to calculate th e masses of substances and volume s of gases formed durin g electrolysis. Example To d etermin e the mass of magnesium produced at the cathod e when a current of 7.
Determine how long a steady current of 2. Extraction of metals from their ores Electrolysis of the molten ore is used to extract aluminium, and metals above aluminium in the electrochemical series, from their ores see p. Purification of metals electrorefining Electrolysis is used to convert an impure metal into the pure metal, a process also known as electrorefining.
CuS04 aQ I impurities from the anode Figure Electroplating Electroplating is the process by which a thin layer of one metal is deposited on another metal by electrolysis. It is used to protect th e original metal fro m co rrosion, to make it look more attractive or to make an inexpensive metal object appear more valuable.
AgN0 3 aQ Figure Silver, nickel and chromium are the metals most commonly used. Anodising Anodising is a process used to increase th e thickness of an unreactive oxide layer on th e surface of a meta l, usually th e aluminium oxide AI, O ,l laye r o n th e surface of aluminium ob ject s.
The aluminium oxide layer is relatively unreactive and adheres to the object, protecting it aga in st co rros ion. It also read ily abso rb s dyes, so can be attractively coloured. Some reactions occu r very rapidly, such as precipitation. Others occur ve ry slowly, such as th e rusting of iro n and stee l.
Other property changes may occur w hi ch are more eas ily measured. The collision theory for chemical reactions During any chemical reaction, the existing bo nds in th e reactants must break so that new bonds ca n form in th e products. This minimum energy is known as activation energy see p. They must lin e up co rrectly with each other so that bonds can break and reform in th e required way.
Some do not occur with the req uired activation energy and some do not occur with the co rrect orientation of particles. An y colli sio n th at results in a reaction is known as an effective collision. This shape shows that the rate of a reaction decreases as the reaction proceeds. The concentration of the reactant particles is at its highest resulting in the frequency of collision between particles being at its highest.
The concentration of the reactant particles decreases as the reaction proceeds causing the frequency of collision between the particle s to gradually decrease.
At this point, one reactant has been used up and no more of its particles are left to collide. This reactant is known as the limiting reactant and its quantity determines the quantity of products made. Pressure and light also affect the rate of some reactions. Pressure affects reactions if the reactants are in the gaseous state, such as the reaction between nitrogen and hydrogen to form ammonia. Light affects the reaction between methane and chlorine see p.
In all these reactions, if pressure or light intensity increase, the rate of reaction increases. A combi nation of the two increases the chances of effective co lli sions. Surface area The smaller the The reaction occurs In flour mills and coal mines the particle size particles of a on the surface of flour and coal dust are extremely reactant, the faster a solid.
Small solid flammable. A slight spark can start a the reaction. Decreasing divided flour and coal particles. As a result, the particles collide more frequently, increasing the chances of effective collisions. As a result, more co lli sions occu r with enough activation energy for th e particles to react, in creasi ng the chances of effective co lli sio ns. The effect of changing different factors on rate curves The effect of changing any factor which alters the rate of a reactio n ca n be shown on the rate curve fo r the reaction.
Both curves become horizontal when th e same amount of product has been made sin ce the number of moles of the lim iting reactant was unchanged. Decreasing the concentration of the reactant in excess, the temperature of th e reaction, th e surface area of a solid reacta nt, or adding a negative cata lyst would ca use th e curve to have a shallower gradient than the original rate curve, become horizontal later, but become hori zontal w h en th e same amount of product has been mad e.
A known volume and concentration of hydrochloric acid was placed into a conical flask, the flask was placed on a balance and excess magnesium filings were added. When a chemical reaction occurs, th ere is usually a change in energy between the reactants and products.
This is normally in the form of heat energy, but may also be in the form of light, nuclear or electrical energy. Exothermic reactions include neutralisation reactions, burning fossil fuels and respiration in cells. An endothermic reaction absorbs heat which causes the reaction mixture and its surroundings to get colder it absorbs energy from the surroundings.
Endothermic reactions include dissolving ce rtain salts in water, thermal decomposition reactions and photosynthesis in plants. Energy is absorbed when the existing bonds in the reactants are broken. Enthalpy changes during reactions The energy content of a substance is called its enthalpy H and cannot be measured directly. Howeve r, it is possible to measure the enthalpy change ,1. H during a reaction. H is usually expressed in kilojoules kJ , or kilojoules per mol kJ mol-'. H is less than zero.
H is negative -ve. The extra energy from the reactants is released to the surroundings. H is greater th an zero. The ext ra energy ga ined by th e products is absorbed from the surroundin gs.
The diagram includes th e enthalpy of th e reactants and products, the enthalpy change tJ. H , and the activation energy. Activatio n energy can be th o ught of as the energy barrier of a reactio n. H wi th the value of tJ. H written alongsid e. A reactio n in which a catalyst is used to in crease the rate has a lower activation energy than th e same reacti on without a catalys t see Tabl e The effect of using a catalyst can be shown on e ne rgy profile diagrams.
To determine th e heat of reaction, the reaction is carried out in an in sulated container called a calorimeter. Th e temperatures of th e reactant s are m easured befo re mixi ng. The maximum or min imum temperature reached when the reactants are mixed is th en measured and used to determine th e teml'erature change. Three assuml'tions are made in calculating the heat of reaction: The density of a dilute aqueou s so lution is the sa m e as pure water, 1 g cm-'. Thi s m ea ns that 1 cm' of so lution has a mass of 1 g.
The sl'ecific heat cal'acity of a dilute aqueous solution is th e same as pure water, 4. This means that it requires 4. A negligible amount of heat is lost to, or ab sorbed from, the surroundings during the reacti o n. Th is absorbs energy fro m th e surro undings. Thi s absorbs energy from th e surro undin gs. Thi s releases energy to th e surro undings.
The reactio n is exothermic if th e en ergy absorbed to brea k b o nd s in th e solute and so lve nt is less than the energy released during sol va ti o n. The reacti o n is endothermic if th e energy absorbed to brea k bonds in the solute and so lvent is greater th an th e energy released during sol vation. When determin ing th e h eat o f soluti on, th e initial temperatu re of th e w ater and the maximum o r minimum temperature o f th e solution mu st be measured.
The temperature increase o r decrease and th e number of moles of solute th at di ssol ved mu st th en be ca lculated. D isso lvi ng Calculate th e heat of solutio n o f potassium nitrate. The reaction w as endothermic. When dete rmin ing the heat of neutralisation, the temperature of both soluti ons must be meas ured and used to determin e the average initial temperature. The maximum temperature of the solu tion after mixing must then be measured and used to calculate the temperature increase.
Fina ll y th e number of moles of water made in the reaction must be determined. The maximum temperature of th e so luti on after mixing is Determine the heat of neutra li sat io n. To determine the number of moles of water made in the reaction: cm ' NaOH aq contains 2. Th e reaction was exothermic. C Draw a fully labelled energy profile diagram for the reaction.
He stirred the solution and recorded a minimum temperature of Lette rs A, B, C and D represent th e processes involved in th ese changes. Give a reason for your answer. Determine the mass of potassium dichromate VI that would crysta lli se out of the so luti on if it is cooled to Give a reason for you r answer.
Your answer should include the following: - A suggested list of the appa ratus he would use. Use this table to answer the following questions. When answering, use the lette rs given in the table as symbols of the unidentified elements; you are not expected to identify the elements. Table 1 Information about three particles. The neutralisation point in the reaction between an aqueous alkali and an aqueous acid can be determined by performing a titration.
Figure 5 shows the burette readings before and after each titration using The experi ment was carried out at room temperature and pressure rtp by adding a fixed mass of c rystal s to excess acid of concen tration 0.
By referring to the ir bonding, exp lain why diamond is a non-conductor and is extremely hard whereas graphite is a good conductor of electricity and is soft and flaky. Explain how this statem ent appli es in EACH of the following reactions. Use the following reactions to support this statement.
When she finally remembers, she finds that the cut surface of each piece has turned brown. Provide a suitable explanation for Granny's observation. Your answer should include relevant equations. Explain the reason for this. Chromium lll sulfate solution is usually used as the electrolyte.
Most organic compounds also contain hydrogen, many contain oxygen and some contain other elements such as nitrogen. Bonding in organic compounds A ca rbon atom has four valence electrons and can therefore form four covalent bonds with other carbon atoms, or atoms of other elements including hydrogen, oxygen, nitrogen and the halogens. Exa mple Met ha ne Formula: CH. The structure of organic molecules The simplest organic molecules can be thought of as being composed of two parts: o The hydrocarbon part composed of only carbon and hydrogen atom s.
The chemical properties of a compound are determined by the reactions of the functional group or groups present. Formulae of organic compounds The formulae of organic compound s can be written in different ways.
The most common ways are: o The molecular formula. This shows the total number of atoms of each element present in one molecule of the compound. This shows how the atoms are bonded in one molecule in a two-dimensional diagramatic form, using a line to represent each covalent bond. Thi s shows the sequence and arrangement of the atoms in one molecule so that the position of attachment and nature of each functional group is shown without drawing the molecule.
This can be condensed further to show the total number of carbon atoms and total number of hydrogen atoms in the hydrocarbon part of the molecule. These are based on Ih e fu nctional group w hich th ey contain. Each homologo us series can be represent ed by a general formula, for example, the general formula of the alkane series is CoH,o. A homologous series is a group of organ ic compounds which all possess the same functional group and can be represented by th e sa m e general formula.
The characterist ics of a homologous series Each homologous series has the fo llow ing characteristics: o Members of a series all have the sa me functional group.
As th e mo lar mass num ber of carbon atoms per molecul e increases, the reacti vity decreases. Generally, as molar mass in creases, th e melting po int, boiling point and density increase. How to name the straight chain members of a homologous series Straight chain members of a homologo us series have a nam e co nsisti ng of two parts: o The first part, or prefix, w hich depends on the total number of carbon atoms in one mo lecule. These are cal led structural isomers.
Structural isomers are organic compounds which have the same molecular formula but different structural formulae. Structural isomerism is the occurrence of two or more organic compounds with the same molecular formula but different structural formulae. Each different structural isomer has a different name, and if they contain the same functional group, they belong to the same homologous series.
Isomers formed by branching Carbon chains can have side branches composed of one or more carbon atoms. For this to happen, the molecules must have four or more carbon atoms. To check if two structu res are isom e rs, w rite th e condensed structural formula of each. They have the gen e ral formula Co H2,.
The number of carbon atoms in thi s chain is indicated usin g the co rrect prefix, and th e homologous series t o whi ch th e compound be longs is indicated usin g th e co rrect ending. The compound has the general formula C"H,"", so it belongs to the alkane series which means its name ends in '-ane'.
The isomer is called 2-methylpentane. Isomers formed by changing the position of the functional group A compound is usually drawn so that its functional group is shown at the right hand end of the molecule; however, its position ca n change. This is see n in the alkene and alcohol series Tables Alkanes with four or more carbon atoms show structural isomerism resulting from their ability to form branched chains.
For exa mpl e, the straig ht chain isomer of butane is sometimes ca lled normal butane or n-butane. Wine is extolled as a food, a social lubricant, an antimicrobial and antioxidant, and a product of immense economic significance. But there is more to it than that. When did humans first start producing wine and what are its different varieties? Are wines nutritious or have any therapeutic values—do they have any role in health or are they simply intoxicating beverages?
How are their qualities determined or marketed and how are these associated with tourism? Concise Encyclopedia of Science and Technology of Wine attempts to answer all these questions and more. This book reveals state-of-the-art technology of winemaking, describing various wine regions of the world and different cultivars used in winemaking. It examines microbiology, biochemistry, and engineering in the context of wine production.
Concise synthesis of substituted meridianins. Jenifer T. Vijay, Nandeesh K. Nagalingaiah, Sandhya C. Nagarakere, G. Suresha, Rangappa S. Kanchugarakoppal and Mantelingu Kempegowda. Cogent Chemistry , 1: Fujisawa T et al. A Concise Introduction to Organic. Albert Zlotkis, University of Houston,. Chapters Various functional groups are covered in. Chapters e. Rabinovich and Z. Khavin, Concise Chemistry. Handbook Khimiya, Moscow, [in Russian]. Andrews and R. Keefer, Molecular Complexes In part to provide a more authentic experience of actual lab work, experiments will be done in groups of two or three.
You may choose partners, or you can ask to be assigned to a group. Prior to each lab period, you will need to spend some time reading the Laboratory.
Studying the Sciences. Grades 10 - This book is designed in such a way that it caters to all the questions that a student may have from Inorganic Chemistry. The book is divided into six parts to make it easier for the readers to find out their answers. Special attention has been paid to the various blocks of the periodic table, so are s-blocks, p-blocks and other boxes such as parts, hydrogen, and other topics. It is constantly updated to take into account the latest changes in the curriculum and any recent additions to the curriculum are reflected in this 5th edition.
It is an ideal book for students preparing for competitive exams. Chapter 1. Atomic structure and the Periodic table. Chapter 2. Introduction to bonding. Chapter 3. Chapter 4. The covalent bond. Chapter 5. The metallic bond. Chapter 6. General properties of the elements. Chapter 7. Coordination compounds. Chapter 8. Hydrogen and the hydrides.. Chapter 9. Group 1 — The alkali metals. Chapter
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