Chemistry Report: Experiment 25 Calorimetry PDF

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Experiment 25 Calorimetry

1

Formal Lab Report: Experiment 25 Calorimetry Priscilla Rangel CHEM 1411-001

Experiment 25 Calorimetry

2 Abstract

The main purpose of the Calorimetry experiment is to measure the enthalpy, specific heat capacity, of substances using a calorimeter. Within physical reactions there is a transfer of heat that can be released as an exothermic reaction, or absorbed as an endothermic reaction. The major results for the three quantitative measurements include the average heat energy ( Δ T) within the substances. The specific heat of a metal is the energy needed to change one gram of unknown metal A by 1℃ . The average specific heat of unknown metal A is 55.81 J/g • ℃ . The acid-base reaction is an exothermic reaction that produces heat, and H₂O. The average Δ T฀ in the acid-base reaction was 2487.1 J or 2.4871 kJ/mol H₂O. The dissolution of salt (ammonium nitrate) measures the energy evolved, or absorbed using Δ Hʟᴇ (Lattice Energy) and Δ H฀ᵧ𝒹 (hydration energy). The final results for the average Δ T฀ for the dissolution of salt was  12098. J/mol of salt.

Experiment 25 Calorimetry

3 Introduction

A calorimeter is a measuring object that is used in the process of calorimetry, which is a procedure that measures the heat of physical/chemical changes, and heat capacity. The heat capacity equation, q (heat) = m (mass) × C฀ (specific heat capacity) × ΔT (temp. change), is the fundamental calorimetry equation used throughout this experiment. It is used to establish the relationship between the heat released or absorbed (q), the heat capacity of an object (C), and the change in temperature (Δ T). The relationship between these units is used to evaluate the amount of heat that is necessary to raise the temperature of an object by 1℃. Endothermic and exothermic reactions play a significant role in specific heat capacity as heat can either be absorbed (endothermic), or released (exothermic). An endothermic reaction is a process where there is an increase of enthalpy (heat). This means that the thermal energy will ultimately be absorbed from the surrounding area, which gives endothermic reactions a positive value. Exothermic reactions release heat, and replace weak bonds with stronger ones. The enthalpy change for exothermic reactions is negative because the total energy of the product is less than the energy of the reactants. The use of calorimetry allows the measure of heat in chemical, and physical reactions. This experiment uses exothermic, and endothermic reactions to display the transmission of heat ( Δ T), or enthalpy. The three quantitative measurements of heat include the specific heat of an unknown metal, heat change in an acid-base reaction, and a change in heat associated with the dissolution of salt with H₂O. All of these reactions provide the information needed to find the maximum temperature for each reaction with a linear graph.

Experiment 25 Calorimetry

4 Procedure

These procedures were followed according to the pages 295-298 of the Beran Laboratory Manual. As well as the Exp. 25 Calorimeter slides with audio provided by my instructor. Part A: Specific Heat of a Metal 1. Before beginning any type of procedure, I gathered all the materials needed and prepared the area around me to complete the laboratory. The first measurement that I needed to record was the mass of an empty beaker, and a test tube filled with unknown metal A. I used a scale, and found that unknown Metal A had a mass of 23.497 g. ` 2. After this I weighed the empty calorimeter (two Nestle styrofoam cups), and filled it with about 20 mL of water. The empty calorimeter was measured at 37.608 g, and once the calorimeter was filled with water the mass was 57.403 g. I subtracted these values to find the mass of the water, which was 19.795 g. After this I began to prepare the water and made sure that the thermometer was correctly set up in order to accurately record the temperature. 3. Once everything was set up which includes preparing the hot plate, thermometer, and metal I took the initial temperature of the water in the calorimeter. The initial temperature of the water was recorded at 19.5 ℃. I also recorded the temperature of the boiling water which was 100.2 ℃. After this I allowed the boiling water to stabilize for a few moments before placing unknown metal A into the calorimeter. Once a few moments passed with the metal inside the calorimeter, I measured and recorded the temperature as time went on. The first recorded temperature of the metal was 31.5 ℃, which continued to rise to

Experiment 25 Calorimetry

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32.6 ℃, decreased to 32.5 ℃, and so on. These measurements helped me create a plot graph that took heat lost in the experiment into account, which resulted in a more accurate value. After I plotted the graph I conducted this procedure a second time. Part B: Enthalpy (Heat) of Neutralization for an Acid-Base Reaction 1. Before beginning any type of procedure, I gathered all the materials needed and prepared the area around me to complete the laboratory. Once this was complete, I began to measure the volume and temperature of the HCl. The volume of the hydrochloric acid that I used was 50 mL, and once I recorded this I measured the initial temperature of the acid in the calorimeter which was 21 ℃. 2. After completing the measurements needed for HCL I began to record the data for NaOH. The initial volume of the base was also 50 mL, and the initial temperature of NaOH in the calorimeter was 21.4 ℃. 3. Once I completed steps 1 and 2, I began to prepare for the acid-base reaction. I carefully, but quickly added the acid to the base and swirled the mixture gently. Once this was done, I recorded the temperature and time gradually for a few minutes. For this experiment I found that the temperature increased from 21.2 ℃ to 27.7 ℃, and began to decrease to 27 ℃ as time went on. These temperatures are important as they helped me plot a graph that accounted for any heat lost. After I plotted the graph I conducted this procedure a second time.

Experiment 25 Calorimetry

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Part C: Enthalpy (Heat) of Solution for the Dissolution of a Salt 1. Before beginning any type of procedure, I gathered all the materials needed and prepared the area around me to complete the laboratory. The first measurement I needed for this experiment was the mass of an empty calorimeter, which was 33.904 g. After this I filled the calorimeter with water (20 mL), and recorded the mass which equals 53.865 g. I calculated the difference between the empty calorimeter, and the calorimeter with water and found the mass of water was 19.961 g. 2. Once the calorimeter was prepared, I began to prepare the salt. The known salt I used in this experiment was ammonium nitrate (NH₄NO₃), and I measured the mass of the salt using a weighing boat. The mass of the ammonium nitrate was about 5.443 g. After I completed these measurements I moved on to the next portion of the procedure. 3. On the lab bench I recorded the initial temperature of the water in the calorimeter after it reached equilibrium, and it equaled 21.4 ℃. Once I recorded this temperature I added the ammonium nitrate into the calorimeter, and stirred the mixture. While stirring the mixture I read and recorded the temperature as time passed. The temperature decreased in this reaction starting with 21.4 ℃, to 17.5 ℃, and finally to 10.5 ℃. These measurements allowed me to plot a graph that accounted for heat lost throughout the process of this procedure. After I have plotted the graph I conducted this procedure a second time.

Experiment 25 Calorimetry

7 Results

Part A: Specific Heat of a Metal

TRIAL 1

TRIAL 2

1. Mass of Metal

23.497 g

22.324 g

2. Temperature of Metal

100.2 ℃

100.2 ℃

3. Mass of Calorimeter

37.608 g

37.623 g

4. Mass of Calorimeter + Water

57.403 g

57.514 g

5. Mass of Water

19.795 g

19.891 g

6. Temperature of Water in Calorimeter

19.5 ℃

19.5 ℃

7. Maximum Temperature of Metal/H₂O from Graph

22.7 ℃

22.5 ℃

TRIAL 1

TRIAL 2

1. Temperature Change of Water

3.2 ℃

3℃

2. Heat Gained by Water

264.8 J

248.2 J

3. Temperature Change of Metal

77.5 ℃

77.7 ℃

56.12 J/g • ℃

55.5 J/g • ℃

Calculations for Specific Heat of Metal

4. Specific Heat of Metal

5. Average Heat of Specific Metal

55.81 J/g • ℃

Experiment 25 Calorimetry

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Experiment 25 Calorimetry

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Part B: Enthalpy (Heat) of Neutralization for an Acid-Base Reaction

TRIAL 1

TRIAL 2

1. Volume of Acid

50 mL

50 mL

2. Temperature of Acid

21 ℃

21.5 ℃

3. Volume of NAOH

50 mL

50 mL

4. Temperature of NAOH

21.4 ℃

21.4 ℃

5. Exact Molar Concentration of NAOH

1 mol/L

1 mol/L

6. Maximum Temperature from Graph

27.4 ℃

27.7 ℃

Calculations for Enthalpy (Heat) of Neutralization of Acid-Base Reactions

TRIAL 1

TRIAL 2

1. Average Initial Temperature of Acid and NAOH

21.2 ℃

21.5 ℃

2. Temperature Change

6.2 ℃

5.7 ℃

100 mL

100 mL

100 g

100 g

4.18 J/g • ℃

4.18 J/g • ℃

6. Heat Evolved

51.8 J

47.7 J

7. Moles of OH ¯ Reacted, the Limiting Reactant

.05 mol

.05 mol

.05 kJ/mol H₂O

.05 kJ/mol H₂O

2591.6 kJ/mol H₂O

2382.6 kJ/mol H₂O

3. Volume of Final Mixture 4. Mass of Final Mixture 5. Specific Heat of Mixture

8. Moles of H₂O Formed 9. Δ H฀

10. Average Δ H฀

2487.1 J or 2.4871 kJ/mol H₂O

Experiment 25 Calorimetry

Part C: Enthalpy (Heat) of Solution for the Dissolution of a Salt:

10

TRIAL 1

TRIAL 2

Experiment 25 Calorimetry

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Ammonium Nitrate 1. Mass of Salt

5.447 g

5.275 g

2. Moles of Salt

.068 mol

.066 mol

3. Mass of Calorimeter

33.904 g

33.815 g

4. Mass of Calorimeter + Water

53.865 g

53.873 g

5. Mass of Water

19.96 g

20.06 g

6. Initial Temperature of Water

21.4 ℃

21.4 ℃

7. Final Temperature of Mixture from Graph

29.3 ℃

29.6 ℃

Calculations for Enthalpy (Heat) of Solution for the Dissolution of Salt

TRIAL 1

TRIAL 2

1. Temperature Change of Solution Δ T

9.34 ℃

9.54 ℃

2. Heat Change of Water

779.3 J

799.9 J

3. Heat Change of Salt

16.14 J

15.95 J

4. Total Enthalpy Change

795.4 J

815.85 J

11942.5 J/mol salt

12254.8 J/mol salt

5. Δ H฀

6. Average Δ H฀

12098.7 J/mol of salt

Experiment 25 Calorimetry

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Experiment 25 Calorimetry

13 Discussion

In this experiment, we are measuring the average amount of heat energy that is expressed throughout the experiment. For my discussion I am going to go over the three different equations from each procedure. The calculations for the average specific metal can be found by following this equation, specific heatᴍ = -

Specific heatʜ₂o × massʜ₂o × ΔT ʜ₂o . massᴍ × ΔT ᴍ

Through this equation I was able to

find the average specific metal by plugging the known values into place. This is the equation with the values plugged into place

22.7 × 19.795 × 19.5℃ , 23.497 × 77.5℃

this means that the specific heatᴍ is equal

to 56.12. The next example is the equation was used to solve the Δ H฀ in the acid-base reaction used in the procedure titled Enthalpy (Heat) of Neutralization for an Acid-Base Reaction. The equation is as follows, (enthalpy change) ΔH฀ = - S pecific heatʜ₂o × combined massesᵃ฀฀ᵈ ⁺ ᵇᵃˢᵉ × ΔT . The equation was used to find the value of ΔH฀ by plugging in the appropriate numbers -4.18 × 100 × 6.2, which equals 2591.6 J (2.5916 kJ). The last example was used to calculate the average Δ H฀ of Solution for the Dissolution of a Ammonium Nitrate. The equation used for this procedure is as follows, (−specific heat ʜ₂o × mass ʜ₂o × ΔT ʜ₂o) + (−specific heat ฀ₐ฀฀ × mass ฀ₐ฀฀ × ΔT ฀ₐ฀฀) . mole ฀ₐ฀฀

filled into the correct place the equation equalled 11942.5.

Once the values were

(−4.18 × 19.96 × 7.9 + (−1.74 × 5.447 × 16.14) , .068

which is

Experiment 25 Calorimetry

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Conclusion In conclusion, the results for the average heat capacity for all of these procedures should reflect the endothermic and exothermic properties of heat being absorbed and released in these reactions. The average heat of a specific metal was equal to 55.81 J/g • ℃. The average Δ H฀ was 2487.1 J (2.4871 kJ), and the average Δ H฀ was 12098.7 J/mol salt. These were all found using heat capacity equations, however I am certain the error percentage of my calculations are extremely high. Nevertheless these are the conclusions I have drawn from the results.

Experiment 25 Calorimetry

15 References

Beran, J. A. (2014). Laboratory Manual for Principles of General Chemistry. Hoboken: Wiley. Libretexts. (2020, August 13). Calorimetry and Reaction Enthalpy. Retrieved November 22, 2020, from https://chem.libretexts.org/Bookshelves/General_Chemistry/Book:_General_Chemistry_ Supplement_(Eames)/Thermochemistry/Calorimetry_and_Reaction_Enthalpy...