Investigation to find out what affect the position of a metal in the reactivity series has on its ability to be displaced.
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Johanna Mans 12.2 Enthalpy changes on displacement and the reactivity series Aim To find out what affect the position of a metal in the reactivity series has on its ability to be displaced. Background Information The reactivity of metals is shown in the reactivity series below. Potassium Most reactive Sodium Calcium Magnesium Aluminium Zinc Iron Lead Copper Silver Gold Platinum Least reactive As zinc is higher in the reactivity series than both lead and copper, it will be able to displace them from their compounds. Hypothesis The 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 Justification Apparatus Justification Polystyrene Cup This acted as the calorimeter, and this is an insulator to ensure that it is not effected by the heat changes in the
It is an irritant so if spilt on labcoat or skin, the area should be washed immediately. Diagram Method 1. The calorimeter was set up as shown in the diagram above. This was done by placing a polystyrene cup inside a glass beaker. 25cm³ of 0.2 molar copper sulphate was measured into the calorimeter, using a 25cm³ 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 temperature 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.
C = Specific heat capacity of the surroundings ?T = Temperature change Reaction 1 25 x 4.2 x 24 = -2520 J 2520/1000 = -2.52 kJ Reaction 2 25 x 4.2 x 22 = -2310 J 2310/1000 = -2.31 Kj The values are negative because the reactions are exothermic. Conclusion The 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: · The heat loss could be minimalised by placing a plastic lid over the top of the calorimeter · 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. · 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.
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