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Enthalpy of a Reaction Lab

Enthalpy of a Reaction Lab. To experimentally determine the enthalpy for the reaction between zinc and copper(II) sulfate. Zn (s ) +CuSO 4 (aq )  Cu (s ) +ZnSO 4 (aq ) +217 kJ mol -1. Purpose:

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Enthalpy of a Reaction Lab

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  1. Enthalpy of a Reaction Lab To experimentally determine the enthalpy for the reaction between zinc and copper(II) sulfate

  2. Zn(s)+CuSO4(aq)Cu(s)+ZnSO4(aq)+217 kJ mol-1 Purpose: To experimentally determine the enthalpy of this reaction. The theoretical value for DH is -217 kJ mol-1 Hypothesis: 217 kJ of energy will be released per mole of copper (II) sulfate.

  3. Data collection Temperature (oC) vs time (minutes) graph  Find the final temperature  Extrapolate the cooling curve Find the Initial temperature

  4. Data Collection: Amounts of reactants and initial and final temperatures. Qualitative observations of the substances and the reaction: Observations: The copper(II) sulfate is a blue solution and zinc is a silver grey powder before the reaction. During the reaction….. A little bit of copper(II) sulfate was spilled… blah… blah

  5. Data processing Energy released: Q = cmDT Q = (4.18 J g-1 oC-1) (20.0 g) (46.0 oC) = - 3849.28 J Moles of limiting reactant: Moles zinc = 3.00g/65.38g mol-1 = 0.0459 moles Moles CuSO4 = 1.0M x 0.0200 dm3 = 0.020 moles Enthalpy of the reaction: DH = Q/mole = 3849.28/0.020 = -192464 J/mol DH = -192 kJ mol-1

  6. Data Processing Percent Error Percent error = (Theoretical – Experimental) x 100 Theoretical value Percent error = (-217 kJ mol-1 -192 kJ mol-1) -217 kJ mol-1 = 11.5%

  7. Data Presentation Theoretical and Experimental Enthalpy Values

  8. Conclusion • In this experiment, copper(II) sulfate and zinc were mixed in a coffee cup calorimeter in order to determine the enthalpy of the reaction. The experimental value -192 kJ mol-1 was lower than the theoretical value -217 kJ mol-1 by 11.5%. Clearly some heat was lost during this experiment or some of the limiting reactant was spilled. Blah… blah… • (Notice: The numbers for the experimental, theoretical and percent error are used in the conclusion!)

  9. Evaluation The experimental value -192 kJ mol-1 was lower than the accepted value by 11.5%. There are a couple of possible errors that may have occurred during this experiment…. blah, blah… made the heat loss greater than expected and this resulted in a lower value for the enthalpy. In addition… blah blah… some blah… and this …. In the future, the experiment could be repeated with three trials in a better insulating cup. In addition… .. Know how each error affected the results… Suggest an improvement for each weakness.

  10. Final notes – The report is individual • DO NOT email or share copies of your lab reports or data tables with other people, even if you were in the same group in the lab! • Submit a typed copy to turnitin.com or a hard copy if you hand wrote the report. • Submit the rough notes taken during the lab and the instructions for the lab report. (I need the rubric on the back.)

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