Experiment 4 Lab Report
Experiment 4 Lab Report
Experiment 4 Lab Report
1. GRAPHS: Make proper1 graphs of temperature (°C) vs. time (sec) for each trial. On each graph, show how you
extrapolate the pre-mixing and post-mixing lines to derive initial and final temperatures, Tinitial and Tfinal, at
the mixing time and show the calculation of T. NOTE: These graphs are to be included in your report.
T (from graph) Trial 1 Trial 2
2. TRIAL CALCULATIONS: Show sample calculations for Trial 1, then give the result for each trial on the
spaces provided.
(a) Mass of final aqueous solution Trial 1 Trial 2
(b) Total heat gained by the water (from T) Trial 1 Trial 2
1
You must use separate sheets of proper graph paper (e.g., customgraph.com/piart.php?art=170, with 20 increments per inch grid) for each
graph. You must select axes scales so that each graph fills the page. Data points and extrapolated lines must be within the grid borders.
You must clearly title the graphs and label the axes, including units. The graphs must be large enough so that they can be read as
accurately as the data from which they were prepared. See Appendix VI of the Lab Manual for more information about graphing.
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CHEM 111 EXPERIMENT 4
Part II: Enthalpy of Solution of NH4Cl(s), H soln
Complete the equation for the physical process, including the physical states of each substance.
(reactant) (product)
Density of the aqueous solution at room temperature:
1. GRAPHS: Make proper graphs1 of temperature (°C) vs. time (sec) for each trial. On each graph, show how you
extrapolate the pre-mixing and post-mixing lines to derive Tinitial and Tfinal and show the calculation of T.
NOTE: These graphs are to be included in your report.
(b) Total heat lost by the water (from T) Trial 1 Trial 2
1. Complete the equation for the chemical reaction representing the formation of NH4Cl(s).
+ + NH4Cl(s)
CHEM 111 EXPERIMENT 4
2. Using Hess’ Law, combine your average H results from Parts IA and IB and the following H° data to calculate the
H of formation for NH4Cl(s). Show your work explicitly.
H° (kJ)
NH4Cl(s) NH4Cl(aq)
1 3
N2(g) + H2 (g) NH3(g) –45.77
2 2
1 1
H2(g) + Cl2 (g) HCl(g) –92.31
2 2
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Report the calculated value of H of
NH4 f Cl(s), using your experimental data.
NOTE: include proper units and sig figs.
3. From a table of thermodynamic data in the Chem 110 textbook (refer to Appendix VIII of the Lab Manual for a
o
specific reference) look up the value of H f of NH4Cl(s).
4. Write the mathematical equation for calculating percent error and show specifically how you use that equation to
o
calculate the percent error between your calculated result and the textbook value for H f of Cl(s).
NH4
Part III: Enthalpy of Solution of an Unknown Compound Unknown Number
Density of the aqueous solution at room temperature:
A. GRAPHS: Make proper1 graphs of temperature (°C) vs. time (min) for each trial. On each graph, show how
you extrapolate the pre-mixing and post-mixing lines to derive Tinitial and Tfinal and show the calculation of
T. NOTE: These graphs are to be included in your report.
T (from graph) Trial 1 Trial 2
B. TRIAL CALCULATIONS: Show sample calculations for Trial 1, then give the result for each trial on the
space provided.
1. Mass of final aqueous solution Trial 1 Trial 2
2. Total heat lost or gained by the water (from T) Trial 1 Trial 2
C. AVERAGE CALCULATION: Show the calculation for the average enthalpy change of solution per gram (in kJ/g)
DISCUSSION OF ERRORS AND CONCLUSION: Describe several different possible sources of experimental error and
give a conclusion for each part of the experiment. (Use separate paper, if you need more space to write.)