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DETERMINING ‘G’
Conclusion: Gravitational acceleration was found to be _____ form the result calculations and _____ form graphical solution. These values were ____% off the accepted value of 9.8m/s^2. the independent variable in this investigation was the length of the string and, therefore, the length of the pendulum this is only if the dimensions of the mass carrier are kept constant which in this case were. SOLUBILITY OF CARBON DIOXIDE, EXPLAINED IN TERMS OF LE CO2 (g) + H2O (l) −↽−⇀− H2CO3 (aq) + Heat. Using the above equilibrium as a practical example of Le Chatelier’s principle: An increase in the concentration of CO2 (g) will shift the equilibrium to the right, converting carbon dioxide and water into carbonic LE CHATELIER’S PRINCIPLE 2.2.4 Identify factors which can affect the equilibrium in a reversible reaction. Le Chatelier’s principle is one which plays a crucial role in the HSC Chemistry course. Thus, a sound understanding of it is important, and it may appear again in this subject depending upon what Option you do. PRACTICALS – RELIABILITY, ACCURACY, VALIDITY AND ERRORS VALIDITY (fairness) A procedure is valid if it tests what it is supposed to be testing. A procedure is invalid if the method of the experiment is incorrect or partially incorrect. In a valid experiment all variables are kept constant apart from those being investigated, all systematic errors have been eliminated and random errors have been HEAT OF COMBUSTION OF ALKANOLS Place the thermometer in the water and record its initial temperature. Light the wick and stir the water gently (to ensure uniform heating). When the temperature has risen 10C extinguish the flame by placing the cap. Again weigh the burner (final mass). Remove any soot from the bottom of the vessel and replace the water before testing the next FARADAY AND LENZ’S LAW By Faraday’s Law as there is a change in flux and relative motion between a magnet and a conductor, emf is induced. As it is a closed circuit, current is formed. This current will flow to oppose the change in flux that induced it by Lenz’s Law. Thus by using right hand grip rule, the current will flow anticlockwise as viewed from themagnet.
FARADAY AND LENZ’S LAW Updated website at: Faraday’s Law of induction states that “The induced electromotive force in any closed circuit is equal to the negative of the time rate of change of the magnLENZ’S LAW
Posts about Lenz’s Law written by celeste SCIENCEHSC | YOUR HSC RESOURCES FOR MATHS 2U/3U/4U Use the equation g = 4π2l/T2 and determine g for each result and finally perform necessary calculation to determine the average. Represent the results graphically by plotting a graph for period squared vs. length. Draw the line of best fit. Use the gradient of CHEMISTRY | SCIENCEHSC Updated website at: Production of materials Heat of combustion of alkanols (practical) Acidic Environment Le Chatelier’s Principle Solubility of Carbon Dioxide, explained in terms of Le ChDETERMINING ‘G’
Conclusion: Gravitational acceleration was found to be _____ form the result calculations and _____ form graphical solution. These values were ____% off the accepted value of 9.8m/s^2. the independent variable in this investigation was the length of the string and, therefore, the length of the pendulum this is only if the dimensions of the mass carrier are kept constant which in this case were. SOLUBILITY OF CARBON DIOXIDE, EXPLAINED IN TERMS OF LE CO2 (g) + H2O (l) −↽−⇀− H2CO3 (aq) + Heat. Using the above equilibrium as a practical example of Le Chatelier’s principle: An increase in the concentration of CO2 (g) will shift the equilibrium to the right, converting carbon dioxide and water into carbonic LE CHATELIER’S PRINCIPLE 2.2.4 Identify factors which can affect the equilibrium in a reversible reaction. Le Chatelier’s principle is one which plays a crucial role in the HSC Chemistry course. Thus, a sound understanding of it is important, and it may appear again in this subject depending upon what Option you do. PRACTICALS – RELIABILITY, ACCURACY, VALIDITY AND ERRORS VALIDITY (fairness) A procedure is valid if it tests what it is supposed to be testing. A procedure is invalid if the method of the experiment is incorrect or partially incorrect. In a valid experiment all variables are kept constant apart from those being investigated, all systematic errors have been eliminated and random errors have been HEAT OF COMBUSTION OF ALKANOLS Place the thermometer in the water and record its initial temperature. Light the wick and stir the water gently (to ensure uniform heating). When the temperature has risen 10C extinguish the flame by placing the cap. Again weigh the burner (final mass). Remove any soot from the bottom of the vessel and replace the water before testing the next FARADAY AND LENZ’S LAW By Faraday’s Law as there is a change in flux and relative motion between a magnet and a conductor, emf is induced. As it is a closed circuit, current is formed. This current will flow to oppose the change in flux that induced it by Lenz’s Law. Thus by using right hand grip rule, the current will flow anticlockwise as viewed from themagnet.
FARADAY AND LENZ’S LAW Updated website at: Faraday’s Law of induction states that “The induced electromotive force in any closed circuit is equal to the negative of the time rate of change of the magnLENZ’S LAW
Posts about Lenz’s Law written by celesteMATHEMATICS
Updated website at: 2 UNIT Basic Algebra Circular Functions Exponential and Logs fundamental limit Geometry Inequations (2unit) Inequations Logs and Indicies Probability Quadratic Equations Relatio PHYSICS | SCIENCEHSC 2012 Yr 12 Physics Cath. Trial 2012 Yr 12 Physics Cath. Trial Ans. Yr 12 Physics TRIAL 2008. Yr 12 Physics Trial 2009. Like this:HSC CHEMISTRY
2.2.4 Identify factors which can affect the equilibrium in a reversible reaction. Le Chatelier’s principle is one which plays a crucial role in the HSC Chemistry course. Thus, a sound understanding of it is important, and it may appear again in this subject depending upon what Option you do. EXPERIMENT | SCIENCEHSC Place the thermometer in the water and record its initial temperature. Light the wick and stir the water gently (to ensure uniform heating). When the temperature has risen 10C extinguish the flame by placing the cap. Again weigh the burner (final mass). Remove any soot from the bottom of the vessel and replace the water before testing the next BCS THEORY EXPLAINED The BCS theory of superconductivity explains that lattice distortions at below critical temperatures lead to the formation of Cooper pairs. Bardeen, Cooper and Schrieffer modelled this theory to successfully explain Type I superconductors. Type I superconductors are metals which exhibit superconducting properties at below their critical SCIENCEHSC | YOUR HSC RESOURCES FOR MATHS 2U/3U/4U Your HSC resources for Maths 2U/3U/4U, Physics and Chemistry PENDULUM | SCIENCEHSC Conclusion: Gravitational acceleration was found to be _____ form the result calculations and _____ form graphical solution. These values were ____% off the accepted value of 9.8m/s^2. the independent variable in this investigation was the length of the string and, therefore, the length of the pendulum this is only if the dimensions of the mass carrier are kept constant which in this case were.FARADAY’S LAW
Faraday’s Law of induction states that “The induced electromotive force in any closed circuit is equal to the negative of the time rate of change of the magnetic flux enclosed by the circuit.”. i.e if there is relative motion (or change in flux) between a magnet and a conductor, then an electromotive force (emf) is induced.COOPER PAIRS
Updated website at: http://sciencehsc.com.au The BCS theory of superconductivity explains that lattice distortions at below critical temperatures lead to the THE PHOTOELECTRIC EFFECT AND IT’S USE IN SOLAR CELLS The photoelectric effect is a phenomenon occurring in everyday life. It is the underlying effect in solar cells and photocells (automatic doors). Below is an explanation of how a solar cell works. Essentially, a solar cell is consisted of a junction between a SCIENCEHSC | YOUR HSC RESOURCES FOR MATHS 2U/3U/4U Use the equation g = 4π2l/T2 and determine g for each result and finally perform necessary calculation to determine the average. Represent the results graphically by plotting a graph for period squared vs. length. Draw the line of best fit. Use the gradient of CHEMISTRY | SCIENCEHSC Updated website at: Production of materials Heat of combustion of alkanols (practical) Acidic Environment Le Chatelier’s Principle Solubility of Carbon Dioxide, explained in terms of Le ChDETERMINING ‘G’
Conclusion: Gravitational acceleration was found to be _____ form the result calculations and _____ form graphical solution. These values were ____% off the accepted value of 9.8m/s^2. the independent variable in this investigation was the length of the string and, therefore, the length of the pendulum this is only if the dimensions of the mass carrier are kept constant which in this case were. SOLUBILITY OF CARBON DIOXIDE, EXPLAINED IN TERMS OF LE CO2 (g) + H2O (l) −↽−⇀− H2CO3 (aq) + Heat. Using the above equilibrium as a practical example of Le Chatelier’s principle: An increase in the concentration of CO2 (g) will shift the equilibrium to the right, converting carbon dioxide and water into carbonic LE CHATELIER’S PRINCIPLE 2.2.4 Identify factors which can affect the equilibrium in a reversible reaction. Le Chatelier’s principle is one which plays a crucial role in the HSC Chemistry course. Thus, a sound understanding of it is important, and it may appear again in this subject depending upon what Option you do. PRACTICALS – RELIABILITY, ACCURACY, VALIDITY AND ERRORS VALIDITY (fairness) A procedure is valid if it tests what it is supposed to be testing. A procedure is invalid if the method of the experiment is incorrect or partially incorrect. In a valid experiment all variables are kept constant apart from those being investigated, all systematic errors have been eliminated and random errors have been HEAT OF COMBUSTION OF ALKANOLS Place the thermometer in the water and record its initial temperature. Light the wick and stir the water gently (to ensure uniform heating). When the temperature has risen 10C extinguish the flame by placing the cap. Again weigh the burner (final mass). Remove any soot from the bottom of the vessel and replace the water before testing the next FARADAY AND LENZ’S LAW By Faraday’s Law as there is a change in flux and relative motion between a magnet and a conductor, emf is induced. As it is a closed circuit, current is formed. This current will flow to oppose the change in flux that induced it by Lenz’s Law. Thus by using right hand grip rule, the current will flow anticlockwise as viewed from themagnet.
FARADAY AND LENZ’S LAW Updated website at: Faraday’s Law of induction states that “The induced electromotive force in any closed circuit is equal to the negative of the time rate of change of the magnLENZ’S LAW
Posts about Lenz’s Law written by celeste SCIENCEHSC | YOUR HSC RESOURCES FOR MATHS 2U/3U/4U Use the equation g = 4π2l/T2 and determine g for each result and finally perform necessary calculation to determine the average. Represent the results graphically by plotting a graph for period squared vs. length. Draw the line of best fit. Use the gradient of CHEMISTRY | SCIENCEHSC Updated website at: Production of materials Heat of combustion of alkanols (practical) Acidic Environment Le Chatelier’s Principle Solubility of Carbon Dioxide, explained in terms of Le ChDETERMINING ‘G’
Conclusion: Gravitational acceleration was found to be _____ form the result calculations and _____ form graphical solution. These values were ____% off the accepted value of 9.8m/s^2. the independent variable in this investigation was the length of the string and, therefore, the length of the pendulum this is only if the dimensions of the mass carrier are kept constant which in this case were. SOLUBILITY OF CARBON DIOXIDE, EXPLAINED IN TERMS OF LE CO2 (g) + H2O (l) −↽−⇀− H2CO3 (aq) + Heat. Using the above equilibrium as a practical example of Le Chatelier’s principle: An increase in the concentration of CO2 (g) will shift the equilibrium to the right, converting carbon dioxide and water into carbonic LE CHATELIER’S PRINCIPLE 2.2.4 Identify factors which can affect the equilibrium in a reversible reaction. Le Chatelier’s principle is one which plays a crucial role in the HSC Chemistry course. Thus, a sound understanding of it is important, and it may appear again in this subject depending upon what Option you do. PRACTICALS – RELIABILITY, ACCURACY, VALIDITY AND ERRORS VALIDITY (fairness) A procedure is valid if it tests what it is supposed to be testing. A procedure is invalid if the method of the experiment is incorrect or partially incorrect. In a valid experiment all variables are kept constant apart from those being investigated, all systematic errors have been eliminated and random errors have been HEAT OF COMBUSTION OF ALKANOLS Place the thermometer in the water and record its initial temperature. Light the wick and stir the water gently (to ensure uniform heating). When the temperature has risen 10C extinguish the flame by placing the cap. Again weigh the burner (final mass). Remove any soot from the bottom of the vessel and replace the water before testing the next FARADAY AND LENZ’S LAW By Faraday’s Law as there is a change in flux and relative motion between a magnet and a conductor, emf is induced. As it is a closed circuit, current is formed. This current will flow to oppose the change in flux that induced it by Lenz’s Law. Thus by using right hand grip rule, the current will flow anticlockwise as viewed from themagnet.
FARADAY AND LENZ’S LAW Updated website at: Faraday’s Law of induction states that “The induced electromotive force in any closed circuit is equal to the negative of the time rate of change of the magnLENZ’S LAW
Posts about Lenz’s Law written by celesteMATHEMATICS
Updated website at: 2 UNIT Basic Algebra Circular Functions Exponential and Logs fundamental limit Geometry Inequations (2unit) Inequations Logs and Indicies Probability Quadratic Equations Relatio PHYSICS | SCIENCEHSC 2012 Yr 12 Physics Cath. Trial 2012 Yr 12 Physics Cath. Trial Ans. Yr 12 Physics TRIAL 2008. Yr 12 Physics Trial 2009. Like this:HSC CHEMISTRY
2.2.4 Identify factors which can affect the equilibrium in a reversible reaction. Le Chatelier’s principle is one which plays a crucial role in the HSC Chemistry course. Thus, a sound understanding of it is important, and it may appear again in this subject depending upon what Option you do. EXPERIMENT | SCIENCEHSC Place the thermometer in the water and record its initial temperature. Light the wick and stir the water gently (to ensure uniform heating). When the temperature has risen 10C extinguish the flame by placing the cap. Again weigh the burner (final mass). Remove any soot from the bottom of the vessel and replace the water before testing the next BCS THEORY EXPLAINED The BCS theory of superconductivity explains that lattice distortions at below critical temperatures lead to the formation of Cooper pairs. Bardeen, Cooper and Schrieffer modelled this theory to successfully explain Type I superconductors. Type I superconductors are metals which exhibit superconducting properties at below their critical SCIENCEHSC | YOUR HSC RESOURCES FOR MATHS 2U/3U/4U Your HSC resources for Maths 2U/3U/4U, Physics and Chemistry PENDULUM | SCIENCEHSC Conclusion: Gravitational acceleration was found to be _____ form the result calculations and _____ form graphical solution. These values were ____% off the accepted value of 9.8m/s^2. the independent variable in this investigation was the length of the string and, therefore, the length of the pendulum this is only if the dimensions of the mass carrier are kept constant which in this case were.FARADAY’S LAW
Faraday’s Law of induction states that “The induced electromotive force in any closed circuit is equal to the negative of the time rate of change of the magnetic flux enclosed by the circuit.”. i.e if there is relative motion (or change in flux) between a magnet and a conductor, then an electromotive force (emf) is induced.COOPER PAIRS
Updated website at: http://sciencehsc.com.au The BCS theory of superconductivity explains that lattice distortions at below critical temperatures lead to the THE PHOTOELECTRIC EFFECT AND IT’S USE IN SOLAR CELLS The photoelectric effect is a phenomenon occurring in everyday life. It is the underlying effect in solar cells and photocells (automatic doors). Below is an explanation of how a solar cell works. Essentially, a solar cell is consisted of a junction between aSCIENCEHSC
YOUR HSC RESOURCES FOR MATHS 2U/3U/4U, PHYSICS AND CHEMISTRYMENU
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NEW WEBSITE!
May 6, 2015
by celeste
Hello all!
I’m going to keep this brief. We’ve recently transitioned to a new website. The latest posts will the updated there! HTTP://SCIENCEHSC.COM.AU We will be discontinuing this blog from today onwards.Advertisements
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FARADAY AND LENZ’S LAWApril 4, 2015
by celeste
UPDATED WEBSITE AT: HTTP://SCIENCEHSC.COM.AU Faraday’s Law of induction states that “The induced electromotive force in any closed circuit is equal to the negative of the time rate of change of the magnetic flux enclosed by the circuit.” i.e if there is relative motion (or change in flux) between a magnet and a conductor, then an electromotive force (emf) isinduced.
Lenz’s Law says that if an induced current flows, its direction is always such that it will oppose the change which produced it. THE IMPORTANCE OF LENZ’S LAW Set up an experiment where the north pole of bar magnet is moving into a coil. As there is relative motion between the magnet and the conductor (the coils), an emf is induced by Faraday’s Law. Lenz’s law tells us that the induced emf will flow to oppose the change in flux that induced it, thus it would flow anticlockwise as viewed from the magnet. Now let us consider if the induced current flowedclockwise!
IF the induced current flowed clockwise then the coil would form a south pole (at the end the magnet is entering), and thus attracts the bar magnet, accelerating it. As the bar magnet increases in velocity, so does the magnitude of induced emf, and again it accelerates the bar magnet further. This clearly violates the law of conservation of energy as kinetic energy and electrical energy is being created. That is why induced emf MUST oppose the change in flux that induced it, otherwise it would violate one of the most fundamental laws ofphysics!
EXAMPLE:
From the diagram, we can see a magnet moving towards a coil. By Faraday’s Law as there is a change in flux and relative motion between a magnet and a conductor, emf is induced. As it is a closed circuit, current is formed. This current will flow to oppose the change in flux that induced it by Lenz’s Law. Thus by using right hand grip rule, the current will flow anticlockwise as viewed fromthe magnet.
_As the current will flow to oppose the change in flux that induced it, the current will induce a north pole at X, to repel the magnet. Using right hand grip rule, our thumbs point north and our fingers indicate the direction of current flow. _ Posted in HSC Physics| Tagged
energy , experiment
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, Faraday's Law
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, Lenz
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THE PHOTOELECTRIC EFFECT AND IT’S USE IN SOLAR CELLSDecember 5, 2013
by celeste
UPDATED WEBSITE AT: HTTP://SCIENCEHSC.COM.AU When electromagnetic radiation is shone onto the surface of a metal and if the incident photons are of higher work function than the metal, electrons would be physically ejected. This is due to the photoelectric effect. However more detail is required. A photon of higher energy (thus higher frequency, _E=hf_) than the work function of the metal will elastically collide transferring completely both momentum and energy to an electron on the surface of the metal. This electron will have enough energy to be physically ejected. It is essential to note that : * The energy (or velocity) of the ejected electrons are dependent on the frequency of the incident photons * The quantity of the ejected electrons are dependent on the intensity of the incident photons The threshold frequency is the minimum frequency of electromagnetic radiation to cause electrons to be ejected. Thus below this frequency, no electrons are emitted from the metal. This threshold frequency depends on the metal involved. The kinetic energy of the ejected electron can be measured using a variation of Plank’s formula. Energy=Frequency x Plank’s constant – Work function of metal It is also key to note that although Einstein was the first to correctly explain the photoelectric effect with the help of Plank’s idea of the quantisation of energy, it was Hertz who first observedthis effect.
Continue reading → Posted in HSC Physics| Tagged
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BCS THEORY EXPLAINEDDecember 4, 2013
by
celeste
UPDATED WEBSITE AT: HTTP://SCIENCEHSC.COM.AU The BCS theory of superconductivity explains that lattice distortions at below critical temperatures lead to the formation of Cooper pairs. Bardeen, Cooper and Schrieffer modelled this theory to successfully explain Type I superconductors. Type I superconductors are metals which exhibit superconducting properties at below their critical temperature. All of which are below 30K. Note that the BCS theory cannot explain superconductivity in Type II superconductors (made from ceramics and have much higher critical temperatures) as its structure is more complicated. Examples of Type I superconductors and their critical temperatures:Zinc – 0.85K
Mercury – 4.15K
Tin – 7.72
As the Type I superconductor is cooled to below critical temperature, the lattice vibrations are minimised. An electron passing through the structure will attract the positive lattice, thus distorting the structure. This distortion releases a phonon (a packet of vibrational energy) and creates a net positive area. Another electron is attracted to this area, absorbing the phonon providing it sufficient energy to overcome electrostatic repulsion and joins with the initial electron, forming a Cooper pair. The Cooper pair acts as one particle and can move through the lattice unimpeded, thus there is zero electricalresistance.
If you have any questions feel free to ask in the comments. Posted in HSC Physics| Tagged BCS
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HEAT OF COMBUSTION OF ALKANOLSDecember 4, 2013
by celeste
UPDATED WEBSITE AT: HTTP://SCIENCEHSC.COM.AUDIAGRAM:
METHOD:
* Set up apparatus as shown. * Light the first spirit burner. * Adjust the height of the vessel so that the tip of the flame justtouches the vessel.
* Weigh the burner _(initial mass)_ with its liquid contents andrecord.
* Add 200 mL of cold water to the vessel using a measuring cylinder. Place the thermometer in the water and record its initial temperature. * Light the wick and stir the water gently (to ensure uniformheating).
* When the temperature has risen 10C extinguish the flame by placingthe cap.
* Again weigh the burner _(final mass)_. Remove any soot from the bottom of the vessel and replace the water before testing the nextalcohol.
METHODS TO REDUCING ERROR WHEN DETERMINING HEAT OF COMBUSTION * Ensure the tip of the flame touches the vessel to minimise heat lost to the environment. * Use a copper can or perform experiment in a bomb calorimeter to contain as much heat as possible. Remember there will always be heat loss to the environment thus the energy absorbed by the water is less than the amount of energy released by the fuel combusting. This loss of energy can be considerably large and thus will result in large inaccuracies. Posted in HSC Chemistry, Practicals
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SOLUBILITY OF CARBON DIOXIDE, EXPLAINED IN TERMS OF LE CHATELIER’SPRINCIPLE
April 22, 2013 by
celeste
UPDATED WEBSITE AT: HTTP://SCIENCEHSC.COM.AU _2.2.5_ DESCRIBE THE SOLUBILITY OF CARBON DIOXIDE IN WATER UNDER VARIOUS CONDITIONS AS AN EQUILIBRIUM PROCESS AND EXPLAIN IN TERMS OF LE CHATELIER’S PRINCIPLE This dotpoint is really just an application of Le Chatelier’s principle using the solubility of carbon dioxide as an example. As such, set yourself in the habit for such questions by starting with the equation, and then working through changes in concentration, pressure, volume and temperature. Note that when you have soft drink in a glass or open bottle, you can see bubbles rising in it. This is because the carbon dioxide gas is constantly escaping, thereby constantly favouring the backwards reaction in an attempt to minimise the disturbance to the system. In comparison, a closed bottle of soft drink has no bubbles unless you shake it, because it is in equilibrium. CO2 (g) + H2O(l) −↽−⇀− H2CO3 (aq) + Heat Using the above equilibrium as a practical example of Le Chatelier’sprinciple:
* An increase in the concentration of CO2 (g) will shift the equilibrium to the right, converting carbon dioxide and water into carbonic acid in order to reduce the concentration of carbon dioxide. * An increase in pressure will shift the equilibrium to the right, converting carbon dioxide and water into carbonic acid in order to reduce the pressure. * An increase in the volume of CO2 (g) will shift the equilibrium to the right, converting carbon dioxide and water into carbonic acid in order to reduce the volume of carbon dioxide. Thus the system will attempt to counteract this change by favouring the backwards reaction. * An increase in temperature will shift the equilibrium to the left, converting carbonic acid into carbon dioxide and water in order to reduce the temperature. * An increase in temperature will shift the equilibrium to the left, converting carbonic acid into carbon dioxide and water in order to reduce the temperature. _Remember- Le Chatelier’s principle will ensure that equilibrium is reached once again. However, this new point of equilibrium will not be same as the original point of equilibrium, as the impact was only minimised, not completely reversed. This is the reason why opened soft drinks will go ‘flat’ irreversibly. _ _From The Student’s Guide to HSC Chemistry._ Posted in HSC Chemistry| Tagged
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LE CHATELIER’S PRINCIPLEApril 21, 2013
by celeste
UPDATED WEBSITE AT: HTTP://SCIENCEHSC.COM.AU Dot point notes on Le Chatelier’s principle: −↽− −⇀− represents equilibrium sign (which looks likethis: )
_2.2.3_ DEFINE LE CHATELIER’S PRINCIPLE The symbol for equilibrium is −↽−⇀− and simply means that, in a closed system, the rate of the forwards reaction is equal to the backwards reaction. This simple means that the reactants are converting to products at the same rate that the products are converting back into the reactants. Whilst there appears to be no change on a macroscopic level, the system is continually changing on a microscopic level. This process, known as dynamic equilibrium, results in the concentration of the substances in the system remainingconstant.
According to Le Chatelier’s principle, if a system at equilibrium is disturbed, then the system will adjust itself in order to minimise the disturbance. However, note that the effects of the disturbance are never fully removed. They are only minimised, or lessened to a degree..
.
_2.2.4_ IDENTIFY FACTORS WHICH CAN AFFECT THE EQUILIBRIUM IN AREVERSIBLE REACTION
Le Chatelier’s principle is one which plays a crucial role in the HSC Chemistry course. Thus, a sound understanding of it is important, and it may appear again in this subject depending upon what Option you do. For this reason, a treatment sounder than required for this dotpoint will be provided. Several factors can affect the equilibrium in a reversible reaction. These disturbances to the system can be in the form of changes in concentration, pressure, volume, or temperature.CONCENTRATION
Imagine a system in equilibrium of four compounds, A, B, C, and D. A + B −↽− −⇀− C + D The simplest way of visualising changes in concentration is simply seeing Le Chatelier’s principle as working to minimise any changes made to the equilibrium. As more of A or B is added, then the system will try to minimise the change by converting more A and B into C and D. As such, the equilibrium shifts to the right. Conversely, if more of C or D is added, increasing the concentration of the products, then the system will convert more C and D into A and B, shifting the equilibrium to the left. Note that a system can only minimise a disturbance. It cannotcompletely undo it.
PRESSURE
Imagine a system in equilibrium of four compounds, A, B, C, and D. Unlike the example used to illustrate changes in concentration, the four compounds in this example are gases, and the number of moles of A is two rather than one. 2 A(g) + B(g) −↽−⇀− C(g) + D(g) Determining the affect of changes in the pressure of a system is simply an exercise in counting moles of gases. In the equilibrium above, there are three moles of gas on the left side, and 2 moles of gas on the right. Any increase in pressure will result in the system trying to relieve the pressure by ‘leveling’ the moles of gas within the system. As such, in the above system, an increase in pressure will lead to a shift in the equilibrium to the right. This occurs simply because the system is essentially counteracting the fact that three moles of gas are becoming two moles of gas. Conversely, a decrease in pressure will shift the above equilibrium to the left in an attempt to increase pressure once again. Changes in pressure affect only gases. Increasing the pressure in the following system will lead to equilibrium shifting to the right, as there are two moles of gas on the left side and only one on the right. A(g) + B(g) −↽−⇀− C(g) + D(s).
.
_2.2._ ACIDIC OXIDES AND THE ATMOSPHERE Any change in volume in a gaseous equilibrium is simply a change in pressure. As such, treat increases in volume as decreases in pressure, as there are more moles of gas in the fixed space, and treat decreases in volume as increases in pressure.TEMPERATURE
The effect of Le Chatelier’s principle with changes in temperature can often be confusing. However, simply thinking of heat as either a product or reactant greatly simplifies any problems, as shown in the equilibrium below, where the reaction is endothermic (Absorbs heat in order for the reaction to occur) rather than exothermic (Releasesheat).
A + B + H e a t −↽− −⇀− C + D In the above endothermic equilibrium, an increase in temperature will result in the system working to reduce the temperature by shifting the equilibrium to the right, converting A and B into C and D in order toreduce temperature.
Conversely, a decrease in temperature will shift the equilibrium to the left, converting C and D into A and B in order to produce moreheat.
In the case of an exothermic reaction, the equation will be of the form A + B −↽− −⇀− C + D + H e a t As shown above, treating heat energy as an actual item in the equilibrium is a much simpler method of thinking of a problem. Simply determine whether a reaction is exothermic forwards, i.e. the heat is placed on the right, or endothermic forwards, i.e. the heat is placedon the left.
Remember- Changes in concentration, pressure, volume and temperature will all disturb a system in equilibrium..
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_From the Student’s Guide to HSC Chemistry. Licensed for free distribution under the GFDL. _ Posted in HSC Chemistry| Tagged
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