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Chemistry Lab Report- Determining the Enthalpy of Enthalpy Change, H, for a Redox Reaction (

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Introduction

Chemistry Lab Report- Determining the Enthalpy of Enthalpy Change, ΔH, for a Redox Reaction (DCP, CE Criterion) Aim: The aim of this investigation is to experimentally determine the change in the enthalpy for the following redox (displacement) reaction: Zn (s) + Zn2+(aq) ---->+ Zn2++ Cu (s) Data Collection and Processing Recording Raw Data: Data Table: Time (seconds) (0.1 seconds) Temperature of Cu + Zn2+ Solution (°C) (±0.5°C) Trial 1 Temperature of Cu + Zn2+ Solution (°C) (±0.5°C) Trial 2 0 21 21 30 21 21 60 21 21 90 21 21 120 21 21 150 59 59 180 57 57 210 56 56 240 55 54 270 54 54 300 53 53 330 53 52 360 50 51 390 49 50 420 47 48 450 46 47 480 45 45 Minimum temperature of trial 1: 21 °C Maximum temperature for trial 1:59°C Temperature difference of trial 1: 38 °C Minimum temperature of trial 2: 21 °C Maximum temperature for trial 2:59 °C Temperature difference of trial 2: 38 °C Processing Raw Data: Mass of CuSO4 Solution (g) (±0.05g) Trial 1 25.0 grams Mass of Zinc Powder (g) (±0.05g) Trial 1 4.0 grams Mass of Copper Calorimeter (g) ...read more.

Middle

(±0.05g) + Mass of Zinc Powder (g) (±0.05g) Mass= 25.0g (±0.05g) +4.0g (±0.05g) Mass= 29.0g (±0.05g) Convert to Kg: 29.0g/1000= 0.0290Kg Mr= Cu-1; 63.55 x 1=63.55 S-1; 32.06 x 1=32.06 O-4 16.00 x 4=64.00 Total relative mass of = 63.55 + 32.06 + 64.00 Total relative mass of ethanol= 159.61= 159.6 (to 3 significant figures) Therefore; Number of Moles (Cu + Zn2+) = 29.0g/159.6 Number of Moles (Cu + Zn2+) = 0.1817 moles ΔH of combustion= ΔH /Number of moles ΔH of combustion= 4.6060.1817 moles= 25.34kJ Since this reaction is exothermic there is a negative sign in front of 25.34kJ,therefore ΔH= - 25.34kJ Propagating Error: Dealing with Errors: Analogue instrument: half of the smallest unit readable Digital instrument: the smallest unit readable Water in calorimeter was measured by a beaker first. Beaker: Analogue instrument- half of smallest measurement readable Half of 1 g = +_ 0.5g Multi meter measuring temperature: Digital instrument-smallest unit measurable = 1.0°C Weighting scale: Digital instrument-smallest unit measurable =0.1g %Uncertainty error of mass of Zn=(+_ 0.1g_4.0g) x 100% = 2.5% %Uncertainty error of mass of CuSO4 = (+_ 0.1g_25.0g) x 100% =0.4% Total %Uncertainty error of mass= %Uncertainty error of mass of Zn + %Uncertainty error of mass of CuSO4 Total %Uncertainty error of mass= 2.5% + 0.4%= 2.54% %Uncertainty error of temperature change of Cu + Zn2+ (1°C/ 38.0°C) ...read more.

Conclusion

Naturally, there are always uncertainties in the measuring devices we used; therefore, there is room for error for every measuring device used. However, this weakness is not major compared to the errors in relation to the calorimeter. S Human error: Some insignificant errors include; the transfer of copper sulphate solution from the 25ml beaker to the calorimeter where maybe not all the solution went to the calorimeter and some droplets could have been left behind in the 25ml beaker. Also, the transfer of the zinc powder from the weighing boat to the calorimeter; where some zinc powder might be left over on the weighing boat. Improving the experiment: The weaknesses and limitation suggest that there are improvements, which can be made to improve this experiment. For the closed system used, there was poor insulation for heat to not get lost. Therefore, a more sophisticated calorimeter with maximum insulation could prevent such heat loss. This could prevent energy to be transferred with the outside surroundings. Instead of using a beaker, we could use a pipette to measure the amount of copper sulphate to be used. Also, for the zinc transfer from the weighing boat to the calorimeter, we could use a more solidified zinc powder. The reason for this is that it will be easier for to transfer the zinc to the calorimeter with minimal zinc being left behind. ...read more.

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