University of Cincinnati, Main Campus CHEM 111 Chem21 Labs exp 9

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Chem21Labs http://www3.chem21labs.com/student2/?mode=assign&assignment=196 1/10 About Chem21Labs | Home | Contact Us | Reference Material | Logout Vamsidhar Student Area Vamsidhar is currently log... ged in. This assignment is due at 11:45 PM on 10/27/2015. Any work submitted between that time and 11:45 PM on 10/28/2015 will result in an automatic 10 point deduction. Also, any work submitted between 11:45 PM on 10/28/2015 and 11:45 PM on 10/29/2015 will result in an additional 10 points being deducted for the assignment. ­ PDF Lab Guide ­ Word Lab Guide Your Instructor prefers the use of the following links to instantly modify incorrectly entered Lab data: Total Lab Reset Change Incorrect Data If the links above do not work for you, please click here. Make sure you completely close and restart your browser after following these instructions. If you have entered any of your lab data incorrectly, please use the link below to send a request directly to your TA and Instructor's email inbox which is monitored during normal school hours. Reset Data Request Answer recorded. Online Lab Submission Complete. Check back several days after the due date to view points added by your instructor. Experiment 9 Report Sheet ENTHALPY OF REACTION - HESS'S LAW Total Points = 106 150 Introduction Note: All essay answers throughout the semester must be composed in the html text editor below. If you copy / paste NG 1010/22/2015 Chem21Labs http://www3.chem21labs.com/student2/?mode=assign&assignment=196 2/10 from another source, you may accidentally insert code that will make your lab sheet display improperly for your TA / Instructor (alerting them that the information was copied from some source). If you need to copy / paste from WORD, first copy / paste into a program like NotePad and then copy paste into the text area below. The objective of the experiment is to test Hess's Law by determining the enthalpy of a reaction. It will be achieved by determining the temp changes for a series of chemichal processes, determining the enthalpy changes for the chemichal processes, comparing the enthalpy changes with available literature values, and testing the validity of Hess's Law. The concepts that tie in with the lecture are heat capacity and Hess's Law. The Lab techniques used in this experiment were calculating heat capacity and testing hess's law with enthalpy change and temp change. Experimental Procedure NG 3 The procedure followed was that given in the handout downloaded from chem 21, Exp: 9, pg. 9­1 to 9­12 Results A. Enthalpy Changes - NH4Cl and NaOH Reaction SOLID FIRST Pathway SOLID LAST Pathway Mass of NH4Cl 2.613 g 2.611 g Initial temperature NaOH(aq) 22.37 oC 21.35 oC Initial temperature water 22.24 oC 22.05 oC First Step: Initial temperature 2 22 2. .2 24 4 oC 2 2 2 21 1. .7 7 oC 2 2 Final temperature 18.52 oC 21.67 oC10/22/2015 Chem21Labs http://www3.chem21labs.com/student2/?mode=assign&assignment=196 3/10 Temperature change ­3.72 ­3.72 oC 1 1 ­.03 ­.03 oC 1 1 Heat Capacity 209 209 J / oC 2 2 4 41 18 8. .4 4 J / oC 2 2 q (Note the sign!!) ­777 ­777 J 2 2 ­12.552 ­12.552 J 2 2 Enthalpy change (Note the sign!!) 777 777 J 1 1 12.552 12.552 J 1 1 Second Step: Initial temperature 2 20 0. .4 45 5 oC 2 2 2 21 1. .6 67 7 oC 2 2 Final temperature 21.04 oC 20.36 oC Temperature change .59 .59 oC 1 1 ­1.31 ­1.31 oC 1 1 Heat Capacity 4 41 18 8. .4 4 J / oC [Show More]

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