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Calorimeter Essay, Research Paper

Introduction

A team was sent to the chemical manufacturing division of a small chemical company to help the technicians with experiments. Since the notes written by the technicians were inaccurate and unfinished, all of the experiments they had preformed needed to redone and documented correctly. The head of the company gave the new team the task of trying to figure out why some chemical reactions caused the reaction vessel to get cold and others caused the vessel to get hot. The group constructed “an apparatus to measure the quantity of thermal energy gained or lost during the chemical reactions” (Bellama, 193). This device was called a calorimeter. A series of different reactions were conducted using two different calorimeters. First, hot and cold water tests were preformed. Based on these results the scientists calculated the heat capacities of the calorimeter. The density and specific heat of pure water were used for these calculations. The other tests that were redone and recalculated were: salts in water, precipitation reactions, and acid base reactions. Then the question of whether the solution absorbed or gave off heat can be answered. Also, whether or not the concentration of an acid base reaction made a difference in the heat absorbed or lost can then be resolved. The goal is to determine if the reactions gave off heat or became cold. The factors that affect heat energy changes were identified (Cooper, 103).

Results

The results for the heat capacities of the calorimeters were determined using the hot and cold water tests. Data was gathered from this experiment and calculations were preformed that resulted in the figures shown in table 1.

Table 1 – Heat Capacity of Calorimeter 1 and 2

Calorimeter (s) Trail 1 Trial 2 Average

1 .03 kJ/℃ .03 kJ/℃ 0.03 kJ/℃

2 .053 kJ/℃ .054 kJ/℃ .054 kJ/℃

Salt in water tests were then done using the salts BaCl2 and NaCl in solid form. Then calculations using the data from the experiment were completed enabling us to determine the results found in Table 2.

Table 2: Caliometer 1 – Change in Heat for Salts in Water

∆H in Trial 1 ∆H in Trial 2 ∆H in Trial 3

BaCl2 0.9 kJ/mol 1.2 kJ/mol 0.9 kJ/mol

NaCl 0.6 kJ/mol 1.2 kJ/mol 0.9 kJ/mol

Table 3: Caliometer 2 – Change in Heat for Precipitation Reactions

∆H in Trial 1 ∆H in Trial 2 ∆H in Trial 3

NaCl & AgNO3 -4.4 kJ/mol -2.8 kJ/mol -2.9 kJ/mol

BaCl2 & Na2SO4 1.4 kJ/mol -1.3 kJ/mol -1.6 kJ/mol

Table 4: Calorimeter 2 – Change in Heat for Strong Acid & Base Reactions

Strong Acid & Base ∆H

(1M) HCl & (1M) NaOH -85.0 kJ/mol

(3M) HCl & (3M) NaOH -63.3 kJ/mol

(6M) HCl & (6M) NaOH -79.3 kJ/mol

Table 5: Calorimeter 1 – Change in Heat for Weak Acid & Base Reactions

Weak Acid & Base ∆H

(1M) CH3COOH & (1M) NH4OH -48.4 kJ/mol

(3M) CH3COOH & (3M) NH4OH -50.7 kJ/mol

(6M) CH3COOH & (6M) NH4OH -54.3 kJ/mol

Discussion

Construction of Calorimeters:

Two calorimeters were constructed using two Styrofoam cups, one placed inside the other lined with aluminum, and a square cardboard lid. An ideal calorimeter was a good insulator and would have a low heat capacity; the perfect heat capacity would be zero. To measure the heat capacity hot and cold water tests were done and recorded for the calculations for the heat capacities, which are needed for later tests. In order to perform the calculations in all of the experiments the team used the density and specific heat of water, which would cause error in our results. The results were shown in Table 1 and a sample calculation is shown below.

Sample Calculation for Calculating Heat Capacity of a Calorimeter:

Heat Of Hot H20 (lost) = Heat Of Cold H20 (gained) + the Calorimeter

Heat Of Hot H20 (lost) = SH of H20 x Mass of Water x ∆T

Heat Of Cold H20 (gained) = SH of H20 x Mass of Water x ∆T

Specific Heat of H20 (SH) = 4.184 J/g ℃

Amount of H20 Used = 50 grams

Ti Cold = 23.1 ℃Ti Hot = 81.4 ℃Tf = 50.3 ℃ ∆TCold = 50.3 – 23.1 = 27.2 ℃∆THot = 50.3 – 81.4 = -31.1 ℃

Heat of Cold H20 = 4.184 J/g ℃ x 50 g x 27.2 ℃ = 5690.24 J

Heat of Hot H20 (lost) = 4.184 J/g ℃ x 50 g x -31.1 ℃ = 6506.12 J

6506.12 J = 5690.24 J + Heat gained by Calorimeter

Heat gained by Calorimeter = 815.88 J

Heat Capacity = Heat gained by the Calorimeter / ∆TCold= 815.88 J / 27.2 ℃ = 30.0 J/℃ ( 0.03 kJ/℃ )

The two calorimeters used were consistent in their heat absorption which is proven by the results in Table 1. Since calorimeter 1 had the lowest heat capacity, it was the best of the two calorimeters

Salts in Water Tests:

The first experiment performed was the heats of reaction for salts in water. The results of the salts in water experiment were shown in Table 2. Sodium chloride and barium chloride were picked to conduct the tests for our salts, and preformed in calorimeter one. The initial temperatures of the salts, however, were not factored into our equations. Instead room temperature was used for the initial temperature of the salts; which caused a discrepancy. A sample calculation of ∆H for a salt in water is shown below. These calculations are, also, the same ones done for the following experiments.

Sample Calculation for ∆H for a Salt in Water (Calorimeter One)

Heat Change in the Reaction = Heat Change of Solution + Heat Change of Calorimeter

Heat Change of Solution = Total Mass of Solution * Specific Heat * ∆T

Heat absorbed by Calorimeter = Heat Capacity * ∆T

Total Mass of Solution = 50 g H2O + 5 g NaCl = 55 g

Specific Heat of H2O = 0.004184 kJ/g

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