Determining an enthalpy change of reaction

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Determining an enthalpy change of reaction

Design

Aim

The purpose of this experiment is to determine the enthalpy change for the displacement reaction:

                Zn(s) + Cu2+(aq) → Cu(s) + Zn2+(aq)

        Introduction

By adding an excess of zinc powder to a measured amount of aqueous copper (II) sulphate, and measuring the temperature change over a period of time, you can than calculate the enthalpy change for the reaction.

Requirements

  • safety spectacles
  • pipette, 25 cm3
  • pipette filler
  • polystyrene cup with lid
  • copper (II) sulphate solution, 0.5 M CuSO4 (harmful if swallowed)
  • weighing bottle
  • spatula
  • zinc powder
  • balance
  • thermometer, 0-100°C (0.1° graduations)
  • watch or clock with second hand

        Procedure

  1. Pipette 25.0 cm3 of the copper (II) sulphate solution into a polystyrene cup.
  2. Weigh about 1 g of zinc powder in the weighing bottle. Since this is an excess, there is no need to be accurate.  
  3. Put the thermometer through the hole in the lid, stir and record the temperature to the nearest 0.1 °C every half minute for 21/2 minutes.
  4. At precisely 3 minutes, add the zinc powder to the cup.
  5. Continue stirring and record the temperature for an additional 4 minutes to complete a copy of Results Table 2.1.
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Results Table 2.1

  1. Perform 2 more trials, repeating steps 1-5 two more times.

Data collection and processing

        Raw Data Table:

           Trial 1

           Trial 2

           Trial 3

*Zinc powder was added to the cup.

        Observations:

                

Before we added the zinc, the CuSO4 solution was a bright aqua blue color. The zinc was a fine powder, colored ...

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