Enthalpy changes on displacement and the reactivity series Essay Example

Enthalpy changes on displacement and the reactivity series Essay To find out what affect the position of a metal in the reactivity series has on its ability to be displaced.Background InformationThe reactivity of metals is shown in the reactivity series below.Potassium Most reactiveSodiumCalciumMagnesiumAluminiumZincIronLeadCopperSilverGoldPlatinum Least reactiveAs zinc is higher in the reactivity series than both lead and copper, it will be able to displace them from their compounds.HypothesisThe closer the metal is to zinc, the harder it will be for zinc to displace, eg, iron would be harder for it to displace than silver. This means that less energy will be produced. Therefore, I predict that lead will be harder to displace, and will therefore have the smaller enthalpy change value.Apparatus JustificationApparatusJustificationPolystyrene CupThis acted as the calorimeter, and this is an insulator to ensure that it is not effected by the heat changes in the experiment100 cmà ¯Ã‚ ¿Ã‚ ½ BeakerThis is what the calorimeter is placed in to ensure tha t it doesnt fall over25 cm à ¯Ã‚ ¿Ã‚ ½ PipetteThis is used to ensure accuracy of measurementsPipette FillerThis is a safety measurement, to ensure none of the substances enter the mouth0 100à ¯Ã‚ ¿Ã‚ ½c thermometerThis measures the temperature changes throughout the experimentSmall containerThis is has the zinc powder measured into it accuratelyElectronic scalesThese are to accurately weigh out the zinc powderStopwatchThis is to accurately measure the time in secondsStirrerThis was used to stir the mixture, which encouraged the reactionPowdered ZnThis is added in excess as shown in the calculations. It is a reactant in both experiments0.2M CuSO4This is added in a suitable volume as a reactant in the first experiment0.2M Pb(NO3)4This is added in a suitable volume as a reactant in the second experimentSafety1. Copper sulphate is harmful if swallowed. It can also be an irritant to the eyes and the skin, so a lab coat and goggles should be used whilst handling. Care should be taken t o not inhale any fumes. If any is spilt in the laboratory, water and mineral absorbent should be added to the area.2. Lead Nitrate is toxic, and is harmful by digestion and inhalation of dusts. Care must be taken to ensure it does not get in the eys, so goggles should be worn at all times. It is an irritant so if spilt on labcoat or skin, the area should be washed immediately.DiagramMethod1. The calorimeter was set up as shown in the diagram above. This was done by placing a polystyrene cup inside a glass beaker. 25cmà ¯Ã‚ ¿Ã‚ ½ of 0.2 molar copper sulphate was measured into the calorimeter, using a 25cmà ¯Ã‚ ¿Ã‚ ½ pipette.2. A thermometer was placed in the solution, and the solution was left for one minute to adjust to room temperature. This was timed by a stopwatch.3. During this time, one gram of zinc was measured out into a small container using electronic scales. After the one minute rest, this was added to the calorimeter and the temperature was taken immediately.4. The temp erature was then taken every 30 seconds, and the mixture was stirred occasionally. The results were recorded in the results table below.For the second experiment, the method was the same as in stages 2, 3 and 4. However, in stage one, 0.2 molar lead nitrate solution is used instead. Before being re used, all the equipment needs to be washed out with distilled water.Results TableTime (In seconds)Temperature change with Copper Sulphate (in à ¯Ã‚ ¿Ã‚ ½c)Temperature change withLead Nitrate ( in à ¯Ã‚ ¿Ã‚ ½c)022223022226028269034321203937150434118044422104644Calculations1. CuSO4 + Zn ( ZnSO4 + Cu0.2 Molar25cmà ¯Ã‚ ¿Ã‚ ½There are 0.2 moles in 1000 cmà ¯Ã‚ ¿Ã‚ ½ of Copper SulphateThere are 0.2/1000 moles in 1cmà ¯Ã‚ ¿Ã‚ ½ of Copper SulphateThere are 25(0.2/1000) moles in 25cmà ¯Ã‚ ¿Ã‚ ½ of Copper SulphateThere are 0.005 moles in 25cmà ¯Ã‚ ¿Ã‚ ½ of Copper SulphateDue to 1:1 ratio, 0.005 moles of Zinc would be needed to react with it2. Pb(NO3)2 + Zn ( Zn(NO3)2 + Pb0.2 Molar25cmà ¯Ã‚ ¿Ã‚ ½There are 0.2 moles in 1000 cmà ¯Ã‚ ¿Ã‚ ½ of Lead NitrateThere are 0.2/1000 moles in 1cmà ¯Ã‚ ¿Ã‚ ½ of Lead NitrateThere are 25(0.2/1000) moles in 25cmà ¯Ã‚ ¿Ã‚ ½ of Lead NitrateThere are 0.005 moles in 25cmà ¯Ã‚ ¿Ã‚ ½ of Lead NitrateDue to 1:1 ratio, 0.005 moles of Zinc would be needed to react with it0.005 x 65.4 = 3.20.327 grams are the minimal mass of zinc needed. As it was needed in excess, 1 gram of zinc was used.2. In order to find the enthalpy changes for the two displacement reactions, the following equation is needed:Q = MC?TIn this equation:Q = Enthalpy changeM = Mass (of solution)C = Specific heat capacity of the surroundings?T = Temperature changeReaction 125 x 4.2 x 24 = -2520 J2520/1000 = -2.52 kJReaction 225 x 4.2 x 22 = -2310 J2310/1000 = -2.31 KjThe values are negative because the reactions are exothermic.ConclusionThe results suggest that the further apart the results are in the reactivity series, the larger the enthalpy change will be. The results could be further improved in several ways:à ¯Ã‚ ¿Ã‚ ½ The heat loss could be minimalised by placing a plastic lid over the top of the calorimeterà ¯Ã‚ ¿Ã‚ ½ Using a higher grade of equipment. For example, the pipette was grade B, and more accurate results could be achieved by using a higher grade of equipment.à ¯Ã‚ ¿Ã‚ ½ Repeating both experiments and then taking mean values. This would smooth out any anomalous results.It must be understood that the results are only accurate to a certain degree because of the equipment. The scales only weigh to 2 decimal places, and the automatically round up. This means the results could be up to 0.009 figures out.