Leggi di Lavoisier e di Proust - in inglese - Popolis

Date: 05/21/08 Student: Comincini Laura Class: 1^ F Year 2007/2008The Lavoisier’s law and the Proust’s law1) Purpose of the experimentTo verify experimentally the Lavoisier’s law and the Proust’s law managing an endothermicchemical reaction that involves the iron and the sulphur.2) Apparatus used to do the laboratory experience- digital electronic - small glasses -container with -container with -steel spoonbalance containers sulphur iron- glass test tube -magnet -gas stove - weight -sheet of white paper- vertical frame provided -funnel - thin glass stickwith a woodden clamp3) Scheme of the assembled apparatus usedproductThe mixing

4) Brief theoretical premiseThe Lavoisier’s law affirms that, during a chemical reaction, the mass does not change.m reagent= m products: “nothing is created, nothing is destroied, but only transformed.”The Proust’s law states that, when two elements react to form a compound they do it according toa defined ratio of masses.5) Description of the stages doing the experience1. Phase: to reset the balance (optional);2. Phase: to put the empty small glass container on the digital electronic balance A) and to reset it;3. Phase: to value the mass of the iron (1g) on the balance setting it into the small glass containerB)4. Phase to repeat the phase 2 with the other small glass container A).5. Phase to value the mass of the sulphur (0,57g) C) putting it into the other small glass containerplaced on the balance;6. Phase: to weigh the empty test tube D);7. Phase: to put the iron and the sulphur into the test tube using the funnel and with a thin glassstick to mix the mixture in order to make it more homogeneous, E);8. Phase: to heat the test tube containing the mixture on the gas stove for about five minutes F);9. Phase: to wait until the chemical reaction occours; later, when the test tube is cooled, take itaway from the gas stove and set it on the balance;10. Phase: to value with the balance the mass of the test-tube containing the ferrous sulphide (FeS)G;)11. Phase: to check if the Lavoisier’ law and the Proust’s law and have been proved;12. Phase: to prove that the test tube with the FeS is attracted by the magnet H) and to break thetest tube with a weight in order to observe the product of the reaction;13. Phase: to gather the data in a table;14. Phase: to calculate the percentage error comparing the mass of the reagent with that on of theproduct.6) Physical quantities measuredQuantity Symbol Units Instrumentmass m (g) Digital electronic Balance7) Characteristics of the instruments used for the data loggingInstrumentResolution CapacityDigital electronic Balance 0,01(g) 1000(g)8) Gathered dataMFe=y1(g) MS=y2(g) M empty test M test tube E%(M)tube=y3 (g) +FeS(g)= y41,00 0,57 15,92 17,49 0

9) Mathematical formulas used for the work out of the gathered datareagentproductFe A=56 1 mol of Fe=56(g)Eac(M)= y4-(y1+y2+y3)S A=32 1 mol of S=32(g)Erc(M)= Eac(M)/y456/56 (g)Fe+32/56 (g)S=1,57(g) E%c(M)= Erc(M)*1001,00(g)Fe + 0,57(g)S =1,57(g)m=15,92(g) Fe+S m=17,49(g) Fe+S +∆Q m=17,49(g)before the reactionafter the reaction10) Final conclusionAnalysis of the experiment and data interpretation- The E%(M) is null and the reaction had entirely occurred.- at the end of the reaction, the mass of the reagents was equal to the mass of the products so thatthe Lavoisier’s law had been confirmed..- breaken the test tube with a weight, the magnet attracted the whole compoud and not only theiron has it happend before the chemical reaction had course. This fact confirms that a newcompound was formed.- We realize also that the Proust’s law had been confirmed; the ratio of combination of theelements had been R=1/0,57Causes of the errorWe did not have any error concerning the mass, but if we should have any it should be due to thefollowing reason: mass loss because part of it (expecially regarding the sulphur) may remain stickedto the glass container; moving of the air during the weighting with the balance; evaporation of thesulphur during the chemical reaction.AdviceFor a better conduction of the experiment in order to get less percentage error (concerning the mass)in the final result, it is advisable to make the mixture the most homogeneous as possible; to lead theexperiment in a place sheltered by the air; before removing the test-tube, to put the residues ofsubstances attached to the small glasses containers into the test tube itself; to wait until the reactionis completed before removing the test-tube from the gas stove.Difficulties to cope with doing this experimentNone.Time required to do the experimentAbout 30 minutes.