Enthalpy Lab Report Essay

1245 Words Apr 28th, 2012 5 Pages
This lab is performed in order to determine the total energy in a reaction between zinc and hydrochloric acid. The reaction is done twice, once to measure the heat of the reaction and again to determine the work done in the system. This is because Enthalpy equals heat plus work (∆H= ∆E+W). Heat and work can be broken down further into separate components so the equation used in lab is ∆H=mc∆T + PV. Many calculations are used in the lab to find out what cannot be measured directly (ex: volume). After all the calculations were complete it was shown to have a very small percent error.

Introduction: The theory behind this experiment is the heat of a reaction (∆E) plus the work (W) done by a reaction is equal to
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The hydrochloric acid is put into a calorimeter and then the zinc is added after. The lid is closed after the zinc is added and a thermometer is inserted through the lid in order to check the temperature as the reaction takes place . The temperature is measured until the reaction has completed and the highest temperature is used as the final temperature. ∆T is then found by the equation ∆T=Tfinal-Tinitial. Then according using the equation ∆H=mc ∆T+PV. In this lab the pressure remains constant while the volume is changing. In order to calculate the volume the same reaction with the same amount of zinc and hydrochloric acid is used. However, instead of a calorimeter, an erhlenmeyer flask with a balloon put over the top is used. The hydrochloric acid is placed into a flask, the zinc is placed inside the balloon and then sealed over the flask. By dropping the zinc into the flask the reaction occurs. This allows the H₂ gas to be captured in the balloon. The circumference of the balloon is then found. The circumference can then be applied to the equation C=2πr and the radius is determined. Using the radius of the balloon, in the equation V=(4/3)πr³ the volume taken up by the hydrogen gas can be found. The pressure is the pressure of the air which is measured with a barometer. ∆H can be found by multiplying the mass of hydrochloric acid, the specific heat of HCl, and ∆T of the hydrochloric

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