ERMINING THE ENTHALPY OF A CHEMICAL REACTION Total Points = Total 20 Lab Data Ca

ID: 1059979 • Letter: E

Question

ERMINING THE ENTHALPY OF A CHEMICAL REACTION

Total Points =

Total

Lab Data

Calibration of Calorimeter

Mass (g) of the styrofoam cup

1.7380

Mass (g) of the styrofoam cup and water (cold water)

24.8444

Mass (g) of 100-mL beaker

50.2266

Mass (g) of 100-mL beaker and water (hot water)

74.0650

Initial temperature (°C) of hot water

51.8

Initial temperature (°C) of the calorimeter and cold water (Click Graph Data to view your Heating Curve)

22.16

Maximum temperature (°C) of the calorimeter and water (Click Graph Data to view your Heating Curve)

34.8114

Reaction 1: Sodium hydroxide + Hydrochloric acid

Volume (mL) of 2.0 M HCl(aq) used

25.00

Initial temperature (°C) of the 2.0 M HCl(aq) (Click Graph Data to view your Heating Curve)

21.53

Volume (mL) of 2.0 M NaOH(aq) used

24.80

Maximum temperature (°C) of the 2.0 M NaOH(aq) (Click Graph Data to view your Heating Curve)

35.8952

Reaction 2: Sodium hydroxide + Ammonium chloride

Volume (mL) of 2.0 M NaOH(aq) used

25.15

Initial temperature (°C) of the 2.0 M NaOH(aq) (Click Graph Data to view your Heating Curve)

20.57

Volume (mL) of 2.0 M NH4Cl(aq) used

24.75

Maximum temperature (°C) of the 2.0 M NH4Cl(aq) (Click Graph Data to view your Heating Curve)

22.4496

Reaction 3: Hydrochloric acid + Ammonia

Volume (mL) of 2.0 M HCl(aq) used

24.90

Initial temperature (°C) of the 2.0 M HCl(aq) (Click Graph Data to view your Heating Curve)

20.6821

Volume (mL) of 2.0 M NH3(aq) used

25.10

Maximum temperature (°C) of the 2.0 M NH3(aq) (Click Graph Data to view your Heating Curve)

36.0597

Lab Results

Three chemical reactions and their associated Enthalpies are investigated in this lab:

Sodium hydroxide + Hydrochloric acid

Sodium hydroxide + Ammonium chloride

Hydrochloric acid + Ammonia

Treat temperature as an exact number when determining significant figures.

Calibration of Calorimeter

1. What was the mass and value of T for the hot and cold water?

Mass (g) of the styrofoam cup

1.7380

Mass (g) of the styrofoam cup and water (cold water)

24.8444

Determine the mass (g) of the water in the cup.

Try 1: 23.11
Try 2: 23.1064

23.1064

0.15

0.25

Mass (g) of 100-mL beaker

50.2266

Mass (g) of 100-mL beaker and water (hot water)

74.0650

Determine the mass (g) of the water in the beaker.

Try 1: 23.8384

23.8384

0.25

Initial temperature (°C) of hot water

51.8

Initial temperature (°C) of the calorimeter and cold water

22.16

Maximum temperature (°C) of the calorimeter and water

34.8114

Determine the T (°C) of the hot water

Try 1: 16.9886
Try 2: -16.9886

-16.9886

0.15

0.25

Determine the T (°C) of the cold water

Try 1: 12.6514

12.6514

0.25

q = msT

Energy = mass × Specific Heat × T

2. Determine the energy released or absorbed by the hot and cold water.

Determine the Energy (J) absorbed (+) or released (-) by the hot water.

Try 1: -1694.441

-1694.441

0.25

Determine the Energy (J) absorbed (+) or released (-) by the cold water.

Try 1: 1261.85
Try 2: 1260
Try 3: 1261

1220

0.3

qcw + qhw +qcal = 0

qcal = heat Capacity x T

3. What is the energy released or absorbed by the calorimeter?

Determine the Energy (J) absorbed (+) or released (-) by the calorimeter.

Try 1: 474.44

474.44

0.35

4. What is the heat capacity of the calorimeter?

Determine the heat capacity (J/°C) of the calorimeter. Remember thatT of the calorimeter will be the same as T of the cold water.

Try 1: 37.5

37.5

0.35

5. What is the heat change (q) for each of the three reactions? Use 1.03 g/mL for the density of all solutions.

6. What is the enthalpy in kJ/mol of the limiting reagent for each of the three reactions?

Reaction 1: Sodium hydroxide + Hydrochloric acid

Volume (mL) of 2.0 M HCl(aq) used

25.00

Initial temperature (°C) of the 2.0 M HCl(aq)

21.53

Volume (mL) of 2.0 M NaOH(aq) used

24.80

Maximum temperature (°C) of the 2.0 M NaOH(aq)

35.8952

Write the balanced chemical equation for this reaction.

0.2

0.25

Determine the T (°C) of the solution surrounding Reaction 1

Try 1: 14.3652

14.3652

0.25

q = msT

q = CT

Energy = mass × Specific Heat × T

Energy = heat Capacity xT

qrxn + qsoln +qcal = 0

We measure the change in temperature of the surrounding solution to determine the change in energy of the solution and use the heat capacity of the calorimeter to account for heat lost to the calorimeter. Heat from the reaction is transferred to the solution and calorimeter, soqrxn= - qsoln- qcal (assuming no heat is lost to the surroundings). The sign on your answer should show whether heat is absorbed (+) or released (-).

Determine the Energy (J) absorbed (+) or released (-) by the solution.

Use the Volume and Density (1.03 g/mL) of the Final Solution to calculate its Mass. The Specific Heat of the Final Solution = 4.18 J/ (g• °C)

Try 1: 61.9
Try 2: 61.8
Try 3: 58.3

3080

0.75

Determine the Energy (J) absorbed (+) or released (-) by the calorimeter (qcal).

Try 1: 185
Try 2: 184943
Try 3: 186

539

0.75

Determine the Energy (J) absorbed (+) or released (-) by the reaction(qrxn)

Try 1: -185659.3
Try 2: -725
Try 3: 725

-3620

0.75

Enthalpy is always reported with respect to a reactant. Calculate the Enthalpy change (kJ/mole), H, for Reaction 1. Your answer should have the correct sign to reflect whether this is an endothermic or exothermic process.

Try 1: 3.6
Try 2: 99
Try 3: 88

-73

0.75

Reaction 2: Sodium hydroxide + Ammonium chloride

Volume (mL) of 2.0 M NaOH(aq) used

25.15

Initial temperature (°C) of the 2.0 M NaOH(aq)

20.57

Volume (mL) of 2.0 M NH4Cl(aq) used

24.75

Maximum temperature (°C) of the 2.0 M NH4Cl(aq)

22.4496

Write the balanced chemical equation for this reaction.

0.5

0.75

Determine the T (°C) of the solution surrounding Reaction 2

Try 1: 1.8796

1.8796

0.25

Determine the Energy (J) absorbed (+) or released (-) by the solution.

Try 1: -393.426
Try 2: -393.
Try 3: 88.1

404

0.75

Determine the Energy (J) absorbed (+) or released (-) by the calorimeter (qcal).

Try 1: 70.5

70.5

0.75

Determine the Energy (J) absorbed (+) or released (-) by the reaction(qrxn)

Try 1: -475

-475

0.75

Enthalpy is always reported with respect to a reactant. Calculate the Enthalpy change (kJ/mole), H, for Reaction 2. Your answer should have the correct sign to reflect whether this is an endothermic or exothermic process.

Try 1: -11.8
Try 2: -5.88
Try 3: -5.8888

-9.44

Reaction 3: Hydrochloric acid + Ammonia

Volume (mL) of 2.0 M HCl(aq) used

24.90

Initial temperature (°C) of the 2.0 M HCl(aq)

20.6821

Volume (mL) of 2.0 M NH3(aq) used

25.10

Maximum temperature (°C) of the 2.0 M NH3(aq)

36.0597

Write the balanced chemical equation for this reaction.

0.25

Determine the T (°C) of the solution surrounding Reaction 3

Try 1: 15.3776

15.3776

0.75

Determine the Energy (J) absorbed (+) or released (-) by the solution

Try 1: 3217
Try 2: 3310

3310

0.75

Determine the Energy (J) absorbed (+) or released (-) by the calorimeter (qcal).

Try 1: -3887
Try 2: 577

577

0.75

Determine the Energy (J) absorbed (+) or released (-) by the reaction(qrxn)

Try 1: -3887

-3887

Jonathan, your calculation is correct!

Enthalpy is always reported with respect to a reactant. Calculate the Enthalpy change (kJ/mole), H, for Reaction 3. Your answer should have the correct sign to reflect whether this is an endothermic or exothermic process.

Try 1: -78.1

-78.1

7. Using Hess's Law and your experimental data from Reactions 1 and 2, determine the Enthalpy change (kJ/mole), H, for Reaction 3.

Tol/Tries(Points)

8. You have two experimental values for the Enthalpy of Reaction 3 - the H calculated from data collected for Reaction 3 and the H calculated from Hess's Law.

Calculate the Percent Error in each of these values compared to the accepted value (calculated previously - Pre-Lab Question 10).

Enter the H (kJ/mole) you calculated in Pre Lab Question 10

Percent Error in Reaction 3's Enthalpy (from mass, Specific Heat and T data collected for Reaction 3).

Enter a Positive Percent Error

Percent Error in Reaction 3's Enthalpy (from Hess's Law).

Enter a Positive Percent Error

Instructor Assigned Grade Based On Percent Error

View Comment

ERMINING THE ENTHALPY OF A CHEMICAL REACTION

Total Points =

Total

Lab Data

Calibration of Calorimeter

Mass (g) of the styrofoam cup

1.7380

Mass (g) of the styrofoam cup and water (cold water)

24.8444

Mass (g) of 100-mL beaker

50.2266

Mass (g) of 100-mL beaker and water (hot water)

74.0650

Initial temperature (°C) of hot water

51.8

Initial temperature (°C) of the calorimeter and cold water (Click Graph Data to view your Heating Curve)

22.16

Maximum temperature (°C) of the calorimeter and water (Click Graph Data to view your Heating Curve)

34.8114

Reaction 1: Sodium hydroxide + Hydrochloric acid

Volume (mL) of 2.0 M HCl(aq) used

25.00

Initial temperature (°C) of the 2.0 M HCl(aq) (Click Graph Data to view your Heating Curve)

21.53

Volume (mL) of 2.0 M NaOH(aq) used

24.80

Maximum temperature (°C) of the 2.0 M NaOH(aq) (Click Graph Data to view your Heating Curve)

35.8952

Reaction 2: Sodium hydroxide + Ammonium chloride

Volume (mL) of 2.0 M NaOH(aq) used

25.15

Initial temperature (°C) of the 2.0 M NaOH(aq) (Click Graph Data to view your Heating Curve)

20.57

Volume (mL) of 2.0 M NH4Cl(aq) used

24.75

Maximum temperature (°C) of the 2.0 M NH4Cl(aq) (Click Graph Data to view your Heating Curve)

22.4496

Reaction 3: Hydrochloric acid + Ammonia

Volume (mL) of 2.0 M HCl(aq) used

24.90

Initial temperature (°C) of the 2.0 M HCl(aq) (Click Graph Data to view your Heating Curve)

20.6821

Volume (mL) of 2.0 M NH3(aq) used

25.10

Maximum temperature (°C) of the 2.0 M NH3(aq) (Click Graph Data to view your Heating Curve)

36.0597

Lab Results

Three chemical reactions and their associated Enthalpies are investigated in this lab:

Sodium hydroxide + Hydrochloric acid

Sodium hydroxide + Ammonium chloride

Hydrochloric acid + Ammonia

Treat temperature as an exact number when determining significant figures.

Calibration of Calorimeter

1. What was the mass and value of T for the hot and cold water?

Mass (g) of the styrofoam cup

1.7380

Mass (g) of the styrofoam cup and water (cold water)

24.8444

Determine the mass (g) of the water in the cup.

Try 1: 23.11
Try 2: 23.1064

23.1064

0.15

0.25

Mass (g) of 100-mL beaker

50.2266

Mass (g) of 100-mL beaker and water (hot water)

74.0650

Determine the mass (g) of the water in the beaker.

Try 1: 23.8384

23.8384

0.25

Initial temperature (°C) of hot water

51.8

Initial temperature (°C) of the calorimeter and cold water

22.16

Maximum temperature (°C) of the calorimeter and water

34.8114

Determine the T (°C) of the hot water

Try 1: 16.9886
Try 2: -16.9886

-16.9886

0.15

0.25

Determine the T (°C) of the cold water

Try 1: 12.6514

12.6514

0.25

q = msT

Energy = mass × Specific Heat × T

2. Determine the energy released or absorbed by the hot and cold water.

Determine the Energy (J) absorbed (+) or released (-) by the hot water.

Try 1: -1694.441

-1694.441

0.25

Determine the Energy (J) absorbed (+) or released (-) by the cold water.

Try 1: 1261.85
Try 2: 1260
Try 3: 1261

1220

0.3

qcw + qhw +qcal = 0

qcal = heat Capacity x T

3. What is the energy released or absorbed by the calorimeter?

Determine the Energy (J) absorbed (+) or released (-) by the calorimeter.

Try 1: 474.44

474.44

0.35

4. What is the heat capacity of the calorimeter?

Determine the heat capacity (J/°C) of the calorimeter. Remember thatT of the calorimeter will be the same as T of the cold water.

Try 1: 37.5

37.5

0.35

Explanation / Answer

Calibration of calorimeter

Mass of Styrofoam cup (g)

1.7380

Mass of Styrofoam cup and water (cold water) (g)

24.8444

Determine mass of water in the cup (g)

23.1064

Mass of 100 mL beaker (g)

50.2266

Mass of 100 mL beak and hot water (g)

74.0650

Determine mass of water in the beaker (g)

23.8384

Initial temperature of hot water (C)

51.8

Initial temperature of calorimeter and cold water (C)

22.16

Maximum temperature of the calorimeter and water (C)

34.8114

Determine T of hot water (C)

-16.9886

Determine T of cold water (C)

12.6514

Determine the energy absorbed or released by the hot water (J) = (mass of hot water)*(sp.heat capacity of water)*T (hot water)

-1694.441

Determine the energy absorbed or released by the cold water (J) = (mass of cold water)*(sp.heat capacity of cold water)*T (cold water)

1223.102

Determine the energy absorbed or released by the calorimeter (J) = (energy released by the hot water) – (energy absorbed by the cold water) (ignore negative sign in case of hot water)

471.339

Heat capacity of calorimeter (J/C) = (energy absorbed by calorimeter)/(temperature of calorimeter and water)

37.256

Reaction 1: Sodium hydroxide + Hydrochloric acid

Volume (mL) of 2.0 M HCl (aq) used

25.00

Initial temperature of 2.0 M (aq) HCl used (C)

21.53

Volume of 2.0 M (aq) NaOH used (mL)

24.80

Maximum temperature of 2.0 M (aq) NaOH used (C)

35.8952

Write the balanced chemical equation for this reaction

HCl (aq) + NaOH (aq) ------> NaCl (aq) + H2O (l)

Determine the T of the solution surrounding Reaction 1 (C)

14.3652

Energy absorbed or released by the solution (J) = (total volume of the solution)*(density of the solution)*(sp. heat of solution)*T

(25.00 mL + 24.80 mL)*(1.03 g/mL)*(4.18 J/g.C)*(14.3562 C) = 3078.097 3078.10

Determine the energy absorbed by the calorimeter (J) = (heat capacity of calorimeter)*T

(37.256 J/C)*(14.3562 C) = 534.85

Determine the energy absorbed or released by the solution (J)

-(3078.10 + 534.85) = -3612.95

Enthalpy of reaction 1 = (energy absorbed/released by the solution)/(moles of limiting reactant) (J/mol)

Limiting reactant = HCl; moles of HCl used = (volume in L)*(concentration in mol/L) = (0.0248)*(2.0) = 0.0496 mol

Enthalpy of reaction = (-3612.95 J)/(0.0496 mol) = -72,841.73 J/mol = -72.84 kJ/mol

Reaction 2: Sodium hydroxide + ammonium chloride

Volume of 2.0 M NaOH (aq) used (mL)

25.15

Initial temperature of 2.0 M NaOH (aq) used (C)

20.57

Volume of 2.0 M NH4Cl (aq) used (mL)

24.75

Maximum temperature of 2.0 M NH4Cl (aq) used (C)

22.4496

Write the balanced chemical equation for the reaction

NaOH (aq) + NH4Cl (aq) ------> NaCl (aq) + NH3 (g) + H2O (l)

Determine the T of the solution surrounding reaction 2 (C)

1.8796

Determine the energy absorbed or released by the solution (J)

(25.15 mL + 24.75 mL)*(1.03 g/mL)*(4.18 J/g.C)*(1.8796 C) = 403.81 J

Determine the energy absorbed or released by the calorimeter (J)

(37.256 J/C)*(1.8796 C) = 70.03 J

Determine the energy absorbed or released by the reaction (J)

-(403.81 + 70.03) = -473.84

Enthalpy of reaction 2

Moles of limiting reactant (NH4Cl) = (0.02475 L)*(2.0 mol/L) = 0.0495 mol.

Enthalpy = -(473.84 J)/(0.0495 mol) = -9572.52 J/mol = -9.57 kJ/mol

Reaction 3: Hydrochloric acid + ammonia

Volume of 2.0 M HCl (aq) used (mL)

24.90

Initial temperature of 2.0 M HCl (aq) used (C)

20.6821

Volume of 2.0 M NH3 (aq) used (mL)

25.10

Maximum temperature of 2.0 M NH3 (aq) used (C)

36.0597

Write the balanced chemical equation for this reaction

HCl (aq) + NH3 (aq) ------> NH4Cl (aq)

Determine the T surrounding reaction 3 (C)

15.3776

Determine the energy absorbed or released by the solution (J)

(24.90 + 25.10)*(1.03)*(4.18)*(15.3776) = 3310.336

Determine the energy absorbed or released by the calorimeter (J)

(37.256)*(15.3776) = 572.91

Determine the energy absorbed or released by the reaction (J)

-(3310.336 + 572.91) = -3883.246

Enthalpy of reaction 3 (J/mol)

Moles of limiting reactant (HCl) = (0.0249)*(2.0) = 0.0498

Enthalpy = (-3883.246/0.0498) = -77976.83 J/mol = -77.976 kJ/mol

7. Write reactions 1 and 2:

HCl (aq) + NaOH (aq) ------> NaCl (aq) + H2O (l) …..(R1)

NaOH (aq) + NH4Cl (aq) -------> NaCl (aq) + NH3 (g) + H2O (l) …..(R2)

(R1) – (R2) gives

HCl (aq) + NaOH (aq) – NaOH (aq) – NH4Cl (aq) ------> NaCl (aq) + H2O (l) – NaCl (aq) – NH3 (g) – H2O (l)

Cancel out common terms and re-arrange to write

HCl (aq) + NH3 (aq) ------> NH4Cl

This is reaction 3. The enthalpy change can be calculated as

Enthalpy change (R3) = Enthalpy change (R1) – Enthalpy change (R2) = -72.84 kJ/mol – (-9.57 kJ/mol) = (-72.84 + 9.57) kJ/mol = -63.27 kJ/mol (ans).

No pre-lab 10 data; hence cannot calculate.

Mass of Styrofoam cup (g)

1.7380

Mass of Styrofoam cup and water (cold water) (g)

24.8444

Determine mass of water in the cup (g)

23.1064

Mass of 100 mL beaker (g)

50.2266

Mass of 100 mL beak and hot water (g)

74.0650

Determine mass of water in the beaker (g)

23.8384

Initial temperature of hot water (C)

51.8

Initial temperature of calorimeter and cold water (C)

22.16

Maximum temperature of the calorimeter and water (C)

34.8114

Determine T of hot water (C)

-16.9886

Determine T of cold water (C)

12.6514

Determine the energy absorbed or released by the hot water (J) = (mass of hot water)*(sp.heat capacity of water)*T (hot water)

-1694.441

Determine the energy absorbed or released by the cold water (J) = (mass of cold water)*(sp.heat capacity of cold water)*T (cold water)

1223.102

Determine the energy absorbed or released by the calorimeter (J) = (energy released by the hot water) – (energy absorbed by the cold water) (ignore negative sign in case of hot water)

471.339

Heat capacity of calorimeter (J/C) = (energy absorbed by calorimeter)/(temperature of calorimeter and water)

37.256

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ERMINING THE ENTHALPY OF A CHEMICAL REACTION Total Points = Total 20 Lab Data Ca

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