Nothing Special   »   [go: up one dir, main page]

Experiment 4 Lab Report

Download as docx, pdf, or txt
Download as docx, pdf, or txt
You are on page 1of 4
At a glance
Powered by AI
The experiment aims to determine the enthalpies of neutralization and solution through calorimetry experiments and use of Hess's Law.

The goal of the experiment is to determine the enthalpies of reaction (ΔH) for neutralization and solution processes through calorimetry and apply Hess's Law to calculate the enthalpy of formation for ammonium chloride.

The steps to determine the enthalpy of neutralization are: 1) Perform calorimetry experiments and construct temperature vs. time graphs, 2) Calculate relevant values such as change in temperature and moles of reactant from the graphs, 3) Determine the enthalpy of neutralization from the calculated values, and 4) Take the average of multiple trials.

CHEM 111 PSU-ABINGTON

Experiment 4 Report Sheet: Enthalpies of Reactions and Using Hess' Law


Your Name: Date: Drawer Number:
Lab Partner’s Name Instructor

Part I: Enthalpies of Neutralization of NH3(aq) and HCl(aq), H neut


Complete the equation for the chemical reaction, including the physical states of each substance.
+
(acid) (base) (product)
Concentration of acid: Concentration of base:
Density of the aqueous solution at room temperature:

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

(c) Total heat of neutralization reaction Trial 1 Trial 2

(d) Moles of limiting reactant neutralized Trial 1 Trial 2

(e) Enthalpy of neutralization, Hneut,


heat per mole of limiting reactant (kJ/mol) Trial 1 Trial 2

3. AVERAGE CALCULATION: Show the calculation for the average H .


neut

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.
Page 1 of 4
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.

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
space provided.
(a) Mass of final aqueous solution Trial 1 Trial 2

(b) Total heat lost by the water (from T) Trial 1 Trial 2

(c) Total heat of solution Trial 1 Trial 2

(d) Moles of NH4Cl dissolved Trial 1 Trial 2

(e) Enthalpy of solution, H ,


soln
heat per mole of NH4Cl (kJ/mol) Trial 1 Trial 2

3. AVERAGE CALCULATION: Show the calculation for the average H


soln
o
Calculation of H for
NH4 f Cl(s)

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)

NH3(aq) + HCl(aq) NH4Cl(aq)

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

NH3(g) NH3(aq) –35.40

HCl(g) HCl(aq) –72.84

o
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

3. Total heat of solution Trial 1 Trial 2

3. Enthalpy change of solution per gram,


heat per gram of unknown compound (in kJ/g) Trial 1 Trial 2

C. AVERAGE CALCULATION: Show the calculation for the average enthalpy change of solution per gram (in kJ/g)

D. Comparison of Unknown to Known Using Enthalpies of Solution


Show how you determined the chemical formula of your unknown compound. (Select the compound given in Table 4.1
whose enthalpy change of solution per gram is the closest to your calculated value.)

Chemical formula of the unknown compound

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.)

You might also like