Friday, March 29, 2019

Determination of coefficient of expansion of air

Determination of coefficient of intricacy of airINTRODUCTIONThis try is based on investigating the coefficient of amplification of air utilize a simple laboratory set up the stopper flask order, where air twinge is constant throughout the try. The increase in peck of a botcholine is directly proportional its temperature increase and is expressed as a fragmentary changed in dimensions per unit temperature change. Air result easily expand when it is heated and contract when it is cooled. The aim of the experiment was to* Determine the coefficient of elaborateness of air using a stoppered flask method.The flask was stoppered and a cryptic tube al minored interactions with the outside. The flask was heated in a beaker (with irrigate system) and then transferred nowadays to insentient irrigate where the cold irrigate was allowed to enter and air deep down the flask decreased. The sign and final intensitys of air and water was compute (directly or indirectly whi chever appropriate) and the coefficient was portendd from these.The experiment in its design allowed the calculation of the coefficient of enlargement of air to be 3.22 * 10-3 K-1. This was calculated at a temperature of 24oC and pressure of 1 atm, which gives a good approximation compared to the a priori lever of 3.37 * 10-3 at a temperature of 24 oC (297 K). THEORYDooley (1919) indicates that turgidnesses are said to be perfectly flexile because they vex no elastic limit and expand and contract equivalent under the action of heat. That is to say, every substance when in the gaseous arouse and not near its point of liquefaction has the same coefficient of involution, this coefficient being 1/273 of its volume for each degree Centigrade.He further goes on to say that since a gas contracts 1/273 part of its volume when its temperature is tear downed 1 C, much(prenominal) a rate of condensate would a priorily reduce its volume to correct at a temperature of 273 C. Sin ce all gases reach their liquefying point before this low temperature is attained, however, no such contraction exists. At the same time, it may be said that if heat is considered as a effect of the molecules of a substance, that motion is to be considered as having ceased when the temperature has reached 273 C.This is the expansion coefficient of an ideal gas.GAY LUSSACS LAWMadan (2008 81) indicates that the coefficient of expansion of a substance at any tending(p) temperature, t, is the small particle of its volume by which one cubic centimeter of the substance entrust increase when heated from to.* Gases are affected by changes of temperature in the same general way as liquids and solids, expanding when heated and contracting when cooled.* For a given change in temperature, they change in volume to a utmost greater extent than either liquids or solids.* All gases, at temperatures comfortably above their liquefying points, have practically the same coefficient of expansio n. This was first observed by Gay Lussac and Charles, and is a very remarkable one, and a great bank line to what has been noticed in the case of solids and liquids, each of which has its own special coefficient of expansion, oftentimes differing widely from those of others. EXPANSION AGAINST CONSTANT PRESSUREAtkins (2006 p35) indicates thatBy definitionAt constant pressureThis indicates that the work done is actually the difference amongst the final and initial volumes multiplied a unit of pressure (which is constant). one time fecal matter say therefore that a gas expands (independent of pressure) but dependent on temperature as given byMETHODMethod as per hand out, however, a small beaker with water was utilise to heat the flask and atmospheric pressure was used instead of reading the barometric top of the inning (which was not available).MATERIALS/APPARATUS Conical Flask (100 mL) Rubber Stopper coat Clip Short Glass Tube Heater Beakers (500 mL) 2 quilted Walled Rub ber Tube Thermometer (0 100oC) Electric Balance weight of flask + fittings136.4 + 0.1 gWeight of flask + fitting + water sucked in168.6 + 0.1 gWeight of water sucked in032.2 + 0.1 gWeight of flask + fittings + full water279.8 + 0.1 gWeight of full water143.4 + 0.1 gTemperature of boiling water103.0 + 0.1 oCTemperature of cold water024.0 + 0.1 oCAtmospheric Pressure1.00 atmVolume of gas 103.0 oC143.4 + 0.1 cm3Volume of gas 24.0 oC111.2 + 0.1 cm3DISCUSSIONThe experiment investigated the coefficient of expansion of air. This economic value was fix to be 3.22 * 10-3 experimentally. One would infer, at first glance, that the volume of air ab initio would have been the volume of the flask (100 mL), as the volume of a gas is the actual volume of the container. But why was the mass of the beaker found (filled with cold water)? Was it to give a better estimation of the volume of the air? By finding the volume using the constriction of water, it was found to be 143.2 cm3 which is a larg e difference compared to the 100 mL of the flask. Then one recognize that the flask was filled to the top close to the stopper itself, and therefore anticipate that the volume of air was 100mL would have been a grave mistake and reckon the volume by density was the best and hi-fi method to use.The experiment relies on the fact that the volume of a substance, in this case, air, is dependent on the temperature of the system. The flask (opened) was heated in boiling water, this was indirect heating of the flask, it allowed the intimate of the flask to be dry and consequently allowed the air to be dry. In addition, by heating the flask in boiling water, the temperature of the air privileged the flask increased as well (according to the zeroth law of thermodynamics), indicating that there will be some form of thermal equilibrium. At this point, the initial volume and temperature of the air will be obtained.The tube was closed with a clip and placed in the water at a lower temperatu re. The question that arises at this point is why was the clip closed? A logical assumption is that to disallow further interaction between the atmospheric air (at a lower temperature) and the flasks air (at a higher temperature), withal one can say that because of the temperature gradient, their will want to escape and in so doing create a thermal equilibrium between the two. The water was allowed to enter, to replace the air and thus the volume of air decreased. This method was preposterous in its design that it used a backward approach. Rather than obtaining the expansion of air from a lower to a higher temperature, it measured the contraction of the air from a higher to a lower temperature. In the end, the initial and final volumes and temperatures of the air being considered were obtained, and thus the coefficient was able to be calculated. deduction OF EXPANSION COEFFICIENTThe value memoriseed experimentally was 3.22 * 10-3. This can be termed a fractional change as it is v ery small (0.001th of a value 3.22). It can be inferred that this fractional change affects the volume of the sample when a rise in temperature occurs. It means therefore, that for every change in temperature from to to (t+1)o, the volume of air in one cm3 of air will increase by 3.22 * 10-3 at 1 atm (experimental condition). A small value of , indicated by Atkins (2006) implies that it responds weakly to changes in temperature i.e. the air responds weakly to changes in temperature which is important in life itself, as air responding strongly to temperature changes would be hazardous to our health, and may even result in cardiac arrests with sudden decreases in temperature (during pass time in north America and Europe among other places) and where there are heat surges.COMPARING EXPERIMENTAL AND THEORETICAL EXPANSION COEFFICIENTThe theoretical value of the expansion coefficient should be, since. The deviation is (3.37 * 10-3- 3.22 * 10-3) = 1.5 * 10-2. This deviation represented al most 4.66% of the theoretical value What can account for this deviation? It all leads to experimental errors, since pressure is constant. Obviously, by looking at the formula, the process of obtaining the final and initial volumes and temperatures will have an effect on the expansion coefficient. The volume of water sucked in may not have been at maximum due to hindrances in the tubing attached to the flask, or the water was not allowed to go in as fast as it should. Also, one can consider that the density of water used to calculate the volume of air after the water had been sucked in may have been different and hence affected the calculated the volume). All of these can contribute uncertainties to the coefficient of expansion and can be used to explain the difference observed.SOURCES OF ERRORS* The difference between the experimental and established determine is therefore attributed to factors such as temperature, volume, and the accuracy at which these values were obtained as des cribed above. * The density of water probably affected the results when it was used to calculate the final volume of air and initial volumes of air. * Within the limits of experimental error, the value ascertained was close to the theoretical value with only about 5% deviation.* The volumes and temperatures had uncertainties of + n, where n represented the volume and temperature. The final result of the coefficient had an uncertainty of 0.41%. LIMITATIONS * The method did not allow the calculations of the volumes and temperatures directly but indirectly. A direct method, if possible, would have contributed to a more accurate value of the coefficient of expansion.* The experiments were not repeated to ascertain different values of the volumes and temperatures. Averaging the values would have allowed a more accurate value of the temperatures and volumes and by extension the coefficient of expansion.ASSUMPTIONS* It was expect that air was ideal in nature and followed the ideal gas equ ation. Introduction of van der waals coefficient would have proved to be more tedious in calculating the coefficient of expansion of air.* It was assumed that the volume of dry air in the flask was the volume of the water in cm3. As mentioned previously, the water was filled to the top of the flask (close to the stopper), and expect 100mL would have been grossly inadequate contributing to more uncertainties and thus a more inaccurate value of the expansion coefficient.* It was assumed that rate at which the temperature and volume decreased when the flask was placed in the water allowed the expansion coefficient to be ascertained. This was very important, as it implied that the temperature affected the expansion and or contraction of air and water which ultimately enabled the calculation of the coefficient.CONCLUSIONWith reference to the aim, it can be concluded that the experiment in its design allowed the calculation of the coefficient of expansion of air to be 3.22 * 10-3 K-1. T his was calculated at a temperature of 24oC and pressure of 1 atm. BIBLIOGRAPHYAnand, A and Negi, S. A Textbook of strong-arm chemistry. USA John Wiley Sons, 1985.Atkins, shaft and De Paula, Julio. 2006. Physical Chemistry 8th Edition. USA W. H Freeman Company, 2006.Castellan and Gilbert. 1983. Physical Chemistry 3rd Edition. Massachusetts Addison Wesley Publishing Company, 1983.Chirlian and L.E. Chemistry 103 Home Page. division of Chemistry 103. Online Cited November 7, 2009. http//www.brynmawr.edu/Acads/Chem/Chem103lc/chem103.html.Daley, Henry and OMalley, Robert. 1988. Problems in Chemistry 2nd Edition. USA CRC, 1988.Dooley, William. utilize Science for Metal Workers. USA Kessinger Publishing, LLC, 2008.Flowers and James. 2004. Cracking the MCAT with CD-ROM. USA Princeton Review, 2004.Haven, Mary, Tetrault, Gregory A and Schenken, Jerald R. 1994. research laboratory Instrumentation 4th Edition. USA Wiley, 1994.Kaufman, Myron. 2002. Principles of thermodynamics . USA CRC, 2002.Lide, David. 1993. Handbook of Chemistry and physical science 74th Edition. USA CRC, 1993.Madan, G.H. An Elementary Treatise on Heat. USA Law Press, 2008.Mortimer, Roger. 2008. Physical Chemistry 3rd Edition. Canada Elsevier Academic Press, 2008.Orme, T. A. An Introduction to the Science of Heat. USA BiblioLife, 2008.

No comments:

Post a Comment