Calorimetry (Experiment 3) Laboratory Report PDF

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Calorimetry Laboratory Report in General Chemistry For Engineers (Laboratory) CM011L...

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Calorimetry (Experiment 3) ABSTRACT Heat and work are the two most common factors for a system to exchange energy with its surroundings. The amount of heat that is released and received in a surrounding is determined by Calorimetry which means anything that is to be measured in terms of heat being generated and exchange with an environment is a possible candidate for calorimetry. This experiment has three (3) objectives: determine the specific heat of a given metal, the enthalpy of neutralization for a strong acid-base reaction and lastly to determine the enthalpy of solution for the dissolution of salt. By the use of a makeshift calorimeter (using a coffee cup Styrofoam) the specific heat of the given metal was measured and if the was heat released or absorbed in the second and third experiments. The measured values were gathered and recorded. The specific heat of metal was determined as 0.2615 (J/g∙°C). The enthalpy of neutralization for a strong acid-base reaction was -50.2 (kJ/mol H2O) for the 2 acids HCl and HNO 3. The enthalpy of solution for the dissolution of salt was 13778.71 (J/mol salt). The experiment was able to adhere to its objectives, determining the specific heat of metal and the enthalpy of both the neutralization for acid-base reaction and the solution for the dissolution of salt. It is recommended in future experiments that a series of trials are practiced to show accuracy and to have precise calculations all the values to be measured must be taken into consideration. Keywords: calorimetry, enthalpy, heat, exothermic, endothermic

INTRODUCTION Heat and work are the two factors in a system that exchange energy with its surroundings. Calorimetry determines the amount of heat released and received in the surrounding. Calorimetry is derived from a Latin word “calor” meaning heat, and a Greek word “metry” meaning to measure. Anything that is to be measured in terms of heat being generated and exchanged in an environment can be used in calorimetry (Chieh, 1996). Exothermic reaction describes when heat is released, and the endothermic reaction describes when heat is absorbed during heat exchange. Calorimeter is used to measure the heat of reaction. According to Beran, 2014, the term enthalpy is used as well to describe heat change in a chemical reaction at constant pressure with the symbol ΔH. In this experiment, a Styrofoam cup was used as the calorimeter because of its chemical components that makes it a good insulated container to prevent heat exchange with the environment. The three objectives for the three parts of the experiment is to first compute and determine the specific heat of the given metal, the enthalpy of neutralization for a strong acid-base reaction, and to determine the enthalpy of solution in the dissolution of salt. MATERIALS AND METHODS

The experiment was divided into three parts wherein part A is the specific heat of metal, part B is the enthalpy of neutralization for an acid-base reaction and part C is the enthalpy of solution for the dissolution of the salt. In order to achieve the objectives of the experiment, the materials such as the Styrofoam cup with lid, beaker, iron stand, thermometer, Bunsen burner and stirring rod were prepared. For the first part of the experiment, a metal with a mass of ten (10) grams was given and placed in the test tube. The beaker was then filled with 300 mL and the Bunsen burner together with the iron rod were set to boil the water. The test tube containing the dry metal was then submerged in the boiling water with the clamp holding it for ten (10) minutes. The mass of the calorimeter (Styrofoam cup) was measured with the digital weighing scale. After recording the weight, it was filled with twenty (20) mL of water and its temperature was measured. After ten (10) minutes, the dry metal was transferred to the calorimeter and was mixed for 5 seconds and the temperature was measured after twenty-five (25) seconds to wait for the metal and the water achieve equilibrium. The temperature was recorded and was used for the computation. Figure 1 shows the measurement of the mass of the calorimeter (Styrofoam cup) with the lead that was used in the experiment and figure 2 shows the test tube containing the dry metal being submerged in the boiling water.

Figure 1. Measurement of Mass of the Calorimeter

Figure 3. Measurement of Volume of NaOH

Figure 2. Test tube with Dry Metal in Boiling Water

Figure 4. Mixing the Acid and the Base

For the second part of the experiment, sodium hydroxide (NaOH) was used as a base and hydrochloric acid (HCl) was used as the acid in the experiment. The researchers used a graduated cylinder to measure fifty (50) mL of sodium hydroxide and transferred the liquid substance inside the makeshift calorimeter then the initial temperature was recorded. At the same time fifty (50) mL of hydrochloric acid was measured in a graduated cylinder and the initial temperature was also recorded. Then, the researchers quickly placed the HCl inside the calorimeter containing the NaOH. The solution was stirred for about five (5) seconds and the temperature was measured after twenty (20) seconds to wait for the solution to achieve equilibrium. The same procedure for the second part was performed but with the use of Nitric Acid (HNO3) as the acid and the data were collected and used for the computations. Figure 3 shows the measurement of the base (NaOH) in the graduated cylinder, figure 4 shows the mixing of the solution and figure 5 shows the measurement of the temperature of the neutralized liquid.

Figure 5. Measurement of Temperature (after 20 s) In the third and last part of experiment which is the determination of the enthalpy of solution for the dissolution of a salt. Five (5) grams of salt was used. Twenty (20) mL of water was measured and transferred in the makeshift calorimeter. Then the salt was placed inside the calorimeter containing the twenty (20) mL water. As for the measurement of the temperature, doing the same procedure as experiment A and B while gently stirring the salt and water until the salt

was dissolved. The temperature was then recorded after twenty (20) seconds and was used for the computation. RESULTS AND DISCUSSION The measured values are presented in table 1. These values are the main values needed for the computation of the specific heat of the given metal. Table 1. Specific Heat of a Metal (Measured Values) Unknown No. M Trial 1 Mass of metal (g) 10 Temperature of metal ( °C) 100 Mass of calorimeter (g) 3.61 Mass of calorimeter + water (g) 23.61 Mass of water (g) 20 Temperature of water in calorimeter 34 (°C) Maximum temperature of metal and 36 water (°C) Temperature change of water, ΔT (°C) 2 Heat gained by water (J) Temperature change of metal ΔT (°C) -64 Specific Heat of metal (J/g∙°C) 0.2615 The calculated values are presented in table 2. The values are computed by using the measurements obtained in table 1. Table 2. Specific Heat of a Metal (Calculated Values) Trial 2 Temperature change of water, ΔT (°C) 2 Heat gained by water (J) Temperature change of metal ΔT (°C) -64 Specific Heat of metal (J/g∙°C) 0.2615 The specific heat of metal was computed by using the equation 1. 𝑆𝑚𝑒𝑡𝑎𝑙 =

(𝑆𝐻2𝑂)(𝑚𝐻2𝑂)(Δ𝑇𝐻2𝑂 ) (𝑚𝑚𝑒𝑡𝑎𝑙)(Δ𝑇𝑚𝑒𝑡𝑎𝑙 )

(1)

The values in table 3 shows the measured values needed for the second part of the experiment followed by table 4 containing the calculated values. Table 3. Enthalpy of Neutralization for Acid-Base Reaction Measured Values (HCl + NaOH) (HNO3 + NaOH)

Volume of acid (mL) Temperature of acid (°C) Volume of NaOH (mL) Temperature of NaOH (°C) Exact molar concentration of NaOH (mol/L) Maximum temperature from graph (°C)

50 34 50 34 1M

50 34 50 34 1M

40

40

Table 4. Enthalpy of Neutralization for Acid-Base Reaction (HCl + (HNO3 + Calculated Values NaOH) NaOH) Temperature change, ΔT (°C) 6 6 Volume of Final Mixture (mL) 100 100 Mass of final mixture (g) 100 100 Specific heat of mixture 4.18 4.18 Heat evolved (J) 2510.4 1673.6 Moles of OH reacted, the 0.05 0.05 limiting reactant (mol) Moles of H 2O formed 0.05 0.05 ΔHn (kJ/mol H2O) -50.2 -50.2 The values calculated in table 4 by inputting the measured values in the formulas shown in equations two (2) and three (3). ΔH𝑟𝑥𝑛 = −(𝑆𝐻2𝑂 )(𝑚𝑎𝑐𝑖𝑑+𝑏𝑎𝑠𝑒 )(ΔT) ΔH𝑛 =

−(𝑆𝐻2𝑂 )(𝑚𝑎𝑐𝑖𝑑+𝑏𝑎𝑠𝑒)(ΔT) (𝑛𝑤𝑎𝑡𝑒𝑟)

(2) (3)

Table 5 shows the values gathered or measured for the third part of the experiment and table 6 contains the computed values from the data in table 5. The moles of salt were computed by using stoichiometry. Table 4. Enthalpy of Solution for the Dissolution of a Salt Measured Values Trial 1 Mass of salt (g) 5 Moles of salt (mol) 0.093 Mass of calorimeter (g) 3.61 Mass of calorimeter + water (g) 23.61 Mass of water (g) 20 Initial Temperature of Water (°C) 34 Final Temperature of Mixture (°C) 20 Table 5. Enthalpy of Solution for the Dissolution of a Salt Computed Values Trial 1 Temperature change of Solution, ΔT (°C) -14 Heat change of water (J) -1171.52

Heat change of salt (J) Total enthalpy change (J) ΔHn (J/mol salt)

-109.9 1061.62 13778.71

The values computed in table 5 were achieved by using the formulas shown in equations four (4) to seven (7).

Chieh, C. (1996). Calorimetry: Measuring Heat Reactions. Retrieved from http://www.science.uwaterloo.ca/~cchieh/cact/c120/calorim etry.html APPENDIX

q 𝐻2𝑂 = 𝑚𝐶(ΔT)

(4)

COMPUTATIONS

q 𝑠𝑎𝑙𝑡 = 𝑚𝐶(ΔT)

(5)

A.

ΔH𝑛 = q 𝐻2𝑂 + q𝑠𝑎𝑙𝑡

(6)

1. ∆𝑇 𝑓𝑜𝑟 𝑤𝑎𝑡𝑒𝑟 = 𝑇𝑓𝑖𝑛𝑎𝑙 − 𝑇𝑖𝑛𝑖𝑡𝑖𝑎𝑙

ΔH𝑟𝑥𝑛 =

[−(𝑆𝐻2𝑂 )(𝑚𝐻2𝑂 )(Δ𝑇𝐻2𝑂 )]+[−(𝑆𝑠𝑎𝑙𝑡 )(𝑚𝑠𝑎𝑙𝑡 )(Δ𝑇𝑠𝑎𝑙𝑡)] (𝑛𝑠𝑎𝑙𝑡 )

(7)

After performing the three parts of the experiment, the change in temperature for each sample were observed. Aligned to the concepts of specific heat and enthalpy, the results obtained were within the range of the specific heat and enthalpy of the materials used in the experiment. CONCLUSIONS AND RECOMMENDATIONS After performing the experiment, the objectives were achieved. The specific heat of metal was determined as 0.2615 (J/g∙°C). The enthalpy of neutralization for a strong acid-base reaction was -50.2 (kJ/mol H 2O) for the 2 acids HCl and HNO3. The enthalpy of solution for the dissolution of salt was 13778.71 (J/mol salt). Although the desired values were obtained in the experiment, there were minimal errors that affected the accuracy of the results in the experiment such as the time lapse of transferring the metal to the calorimeter since the metal stuck to the test tube. Another source of error is the precision of the temperature that was measured.

∆𝑇 = 36℃ − 34℃ ∆𝑇 𝑓𝑜𝑟 𝑤𝑎𝑡𝑒𝑟 = 2℃

2. ∆𝑇 𝑓𝑜𝑟 𝑚𝑒𝑡𝑎𝑙 = 𝑇𝑓𝑖𝑛𝑎𝑙 − 𝑇𝑖𝑛𝑖𝑡𝑖𝑎𝑙 ∆𝑇 = 34℃ − 100℃ ∆𝑇 𝑓𝑜𝑟 𝑚𝑒𝑡𝑎𝑙 = −64℃

3. Heat gained by water 𝑄 = 𝑚𝑐∆𝑇 𝐽 𝑄 = (20 𝑔) (4.184 ) (2℃) 𝑔. ℃

𝑄 = 167.36 𝐽 4. Specific Heat of metal 𝑆𝑝𝑒𝑐𝑖𝑓𝑖𝑐 𝐻𝑒𝑎𝑡𝑚𝑒𝑡𝑎𝑙 = −

REFERENCES Beran, J. (2014). Laboratory Manual for Principles of General Chemistry: 10th Edition. 293-298.

𝑆𝑝𝑒𝑐𝑖𝑓𝑖𝑐 𝐻𝑒𝑎𝑡𝑚𝑒𝑡𝑎𝑙 =

(𝑆𝐻20 )(𝑚𝐻20 )(∆𝑇𝐻20) (𝑚𝑚𝑒𝑡𝑎𝑙 )(∆𝑇𝑚𝑒𝑡𝑎𝑙 ) 𝐽 𝑔. ℃)(20 𝑔)(2℃) (10𝑔)(−64℃)

(4.184

𝑆𝑝𝑒𝑐𝑖𝑓𝑖𝑐 𝐻𝑒𝑎𝑡𝑚𝑒𝑡𝑎𝑙 = 0.2615

𝐽 𝑔. ℃

1. q 𝐻2𝑂 = 𝑚𝐶(ΔT)

B. 1. ∆𝑇 = 𝑇𝑓𝑖𝑛𝑎𝑙 − 𝑇𝑖𝑛𝑖𝑡𝑖𝑎𝑙

q 𝐻2𝑂 = (20𝑔) (4.184

∆𝑇 = 40℃ − 36℃

2. q 𝑠𝑎𝑙𝑡 = 𝑚𝐶(ΔT)

∆𝑇 = 6℃ 2. Heat Evolved for HCI + NaOH amd HNO3 NaOH 𝑄 = 𝑚𝑐∆𝑇

q 𝑠𝑎𝑙𝑡 = (5𝑔) (1.57

𝐽

𝑄 = 2510.4 𝐽

1. Moles of OH 𝑛𝑁𝑎𝑂𝐻 = 𝑉𝑁𝑎𝑂𝐻 𝑥 𝑚𝑁𝑎𝑂𝐻

3. ΔH𝑛 = −q 𝐻2𝑂 + q 𝑠𝑎𝑙𝑡

𝑚𝑜𝑙 𝐿

4. ΔH𝑟𝑥𝑛 [−(𝑆𝐻2𝑂 )(𝑚𝐻2𝑂 )(Δ𝑇𝐻2𝑂 )] + [−(𝑆𝑠𝑎𝑙𝑡 )(𝑚𝑠𝑎𝑙𝑡 )(Δ𝑇𝑠𝑎𝑙𝑡 )] = (𝑛𝑠𝑎𝑙𝑡 ) ΔH𝑟𝑥𝑛 𝐽 𝐽 [(−4.184 𝑔𝐶 )(20𝑔)(−𝟏𝟒𝐂)] + [(−1.57 )(5𝑔)(−𝟏𝟒𝐂)] 𝑔𝐶 = (0.093 𝑚𝑜𝑙 𝑠𝑎𝑙𝑡) 𝐽 = 13.778.71 𝑚𝑜𝑙 𝑠𝑎𝑙𝑡

𝑛𝑁𝑎𝑂𝐻 = 0.05 mol 𝑆𝑖𝑛𝑐𝑒 1 𝑚𝑜𝑙 𝑁𝑎𝑂𝐻 𝑖𝑠 𝑒𝑞𝑢𝑎𝑙 𝑡𝑜 1 𝑚𝑜𝑙 𝑜𝑓 𝑂𝐻 𝑎𝑛𝑑 𝐻20 Moles of OH = 0.05 mol Moles of H20=0.05 mol 2. Enthalpy (heat) 𝐽

𝐸𝑛𝑒𝑟𝑔𝑦 (𝐽) = -𝑆𝑝𝑒𝑐𝑖𝑓𝑖𝑐 𝐻𝑒𝑎𝑡 (𝑔.℃) 𝑋 𝑚𝑎𝑠𝑠 (g) ∆T (℃) 𝐽 ∆𝐻 = 𝑆𝑝𝑒𝑐𝑖𝑓𝑖𝑐 𝐻𝑒𝑎𝑡 (𝑔.℃) 𝑋 𝑚𝑎𝑠𝑠 (g) ∆T (℃)

∆𝐻 =

(−4.184 J/g. C) (100 g ) (6℃) 0.05 𝑚𝑜𝑙 𝐻2𝑂 𝑘𝐽

∆𝐻 = −50.2 𝑚𝑜𝑙 𝐻2𝑂

C.

𝐽 ) (−𝟏𝟒𝐂) = −19.9𝐽 𝑔𝐶

ΔH𝑛 = −(−1171. 52 𝐽) + (−109.9𝐽) = 1061.62 𝐽

𝑄 = (100 𝑔 ) (4.184𝑔.℃) (6℃)

𝑛𝑁𝑎𝑂𝐻 = 0.0500𝐿 𝑥 1

𝐽 ) (−𝟏𝟒𝐂) = −1171.52 𝐽 𝑔𝐶...