# Project #24068 - Hess Law Lab

*****Use a graduated cylinder to accurately measure 10 mL of 2M HCl. Use an empty thin-stem

pipet to remove or add drops of HCl so that the meniscus level is on the 10 mL mark. Pour the

10 mL HCl into the Styrofoam calorimeter. Rinse the thin-step pipet according to this manual’s

instructions on Use, Disposal, and Cleaning of Common Materials.

Rinse and dry the graduated cylinder and accurately measure 10 mL of 2M NaOH using the

same technique in step 2 above. Pour the 10 mL NaOH into another Styrofoam cup and place

the cup into a second empty coffee cup to prevent it from tipping over.

Turn on the digital thermometer and place it into the HCl solution. Wait 5 minutes and record

the temperature of the solution in Data Table 1.*****

That was the measurements of the substances used in this expierement.  I did the actual lab, and filled in the blanks on the data table the best I could.  Need question A-J answered and also need the Average Inital Temperature for each of the 3 Reactions. Also need the Change in Temperature of mixture (triangle T) for each of the 3 Reactions as well.

Hess's Law Lab Report Assistant

Part 1 Reaction HCl & NaOH --> NaCl +H2O

Data Table 1: Sample Data

Initial Temperature of HCL - (degrees C)  21.7

Inital Temperature of NaOH - (degrees C)22.1

Average Inital Temperature - (degrees C) ?

Final Temperature of mixture32.8

(extrapolated)

Change in Temperature of mixture (triangleT)  ?

Data Table 2: Sample Data

Time after mixing-secondsTemperature (degrees C)

2033.5

4033.9

6033.8

8033.8

10033.0

12034.2

14034.2

16033.8

18033.4

20033.3

22033.3

24033.2

26033.2

28032.9

30032.8

Part 2: Reaction 2: NH4Cl+NaOH--> NH3 +NaCl + H2O

Data Table 3:

Initial Temperature of HCL - (degrees C)  22.1

Inital Temperature of NaOH - (degrees C)24.0

Average Inital Temperature - (degrees C) ?

Final Temperature of mixture23.9

(extrapolated)

Change in Temperature of mixture (triangleT)  ?

Data Table 4:

Time after mixing-secondsTemperature (degrees C)

2023.9

4024.0

6024.2

8024.1

10024.2

12024.1

14024.2

16024.0

18024.0

20024.1

22024.1

24024.1

26024.1

28023.9

30023.9

Part 3: Reaction:  NH3+HCl--> NH4Cl

Data Table 5:

Initial Temperature of HCL - (degrees C)  21.7

Inital Temperature of NaOH - (degrees C)25.1

Average Inital Temperature - (degrees C) ?

Final Temperature of mixture31.2

(extrapolated)

Change in Temperature of mixture (triangleT)  ?

Data Table 6:

Time after mixing-secondsTemperature (degrees C)

2030.3

4031.9

6032.1

8032.2

10032.0

12031.9

14031.9

16031.8

18031.8

20031.8

22031.7

24031.6

26031.5

28031.2

30031.2

Questions

For A. through E. See the calculations for the Data Tabes above

A.  Using the data from your data tables calculate (triangleT) for all three reacions.

B.   Calculate the heat loss or gain of the three solutions mixtures:

C.   Use Hess' Law and (triangleH) for the first two reactions:

NaOH(aq)+HCl(aq)--> H2) (l) +NaCl (aq)

NaOH(aq)+NH4Cl(aq)-->NH3+NaCl+H2O(l)

to determine (triangle H) for this reaction: NH3+HCl-->NH4Cl

D.   Compare the results of step 3 aboce with the experimental results of the  Nh3+HCl--> NH4Cl

E.  Use the thermodynamic quantites given below to calculate the theoretical (triangle H) for this reaction: NH3+HCl--> NH4Cl

-   (triangle H ferinhite) for NH3 (aq) = 80.29kj/mol

- (triangle H ferinhite) for HCl (aq) = 167.2 kj/mol

- (triangle H ferinhite) for NH4 (aq) = 132.5 kj/mol

- (triangle H ferinhite) for Cl (aq) = 167.2 kj/mol

F.  What was teh (triangle H) value obtained for NH3+HCl  `a NH4Cl from Hess' Law method?

G.  What was the (triangle H) value obtained for NH3+HCl  `a NH4Cl experimentally?

H.  What was the calculated (triangle H) value obtained for NH3 + HCl  `a  NH4Cl using published thermodynamic data?

I.  What was the % error of the various methods used?  (i.e. comparing the results of the results of Hess' Law method and the experimental results to the calculated value?

J.  Name three examples of the practicle application for the use of (triangle H) values.

 Subject Science Due By (Pacific Time) 03/03/2014 10:59 pm
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