Lab Questions: Experiment 3 Lab Procedures: Take a new calorimeter from the Cont

Question

Lab Questions: Experiment 3

Lab Procedures:

Take a new calorimeter from the Containers shelf and place it on the workbench.

Take water from the Materials shelf and add 25.0 mL to the calorimeter.

Take a thermometer from the Instruments shelf and attach it to the calorimeter. Record the temperature inside the calorimeter in your Lab Notes.

Take ammonium chloride (NH4Cl) from the Materials shelf and add 5.000 g to the calorimeter.

Observe the temperature change in the calorimeter as the reaction proceeds. Record the new temperature your Lab Notes.

Lab Notes:

Experiment 3: Determine the Enthalpy of Dissolution of NH4Cl in Water

Temp of calorimeter + 25 mL water: 21.5 C

Temp of calorimeter + 25 mL water + 5.000 g ammonium chloride: 9.1 C

1. How many moles of NH4Cl did you add to the calorimeter? The molar mass of NH4Cl is 53.49 g/mol.

53.49 moles

0.09348 moles

0.0250 moles

5.000 moles

2. What was the value of qcal for the dissolution of ammonium chloride in water? Choose the closest answer.

181 J

14.6 J

-1740 J

-181 J

-12.4 °C

9.1 °C

12.4 °C

21.5 °C

4. What was the heat of solution (qsoln) for the dissolution of ammonium chloride in water? Choose the closest answer.

1740 J

-1560 J

-1740 J

1560 J

5. Calculate the enthalpy of the dissolution of NH4Cl in water. The molar mass of NH4Cl is 53.49 g/mol. To receive full points for this question, list every step of your calculation.

6. Given the data in the table below, what is the enthalpy of reaction for the following sulphur dioxide synthesis reaction?

7. Given the data in the table below, what is the enthalpy of dissolution of KOH? The molar mass of KOH is 56.11 g/mol, the specific heat of solution is 4.184 J/gºC, and the calorimeter constant is 22.45 J/ºC. To receive full points for this question, list every step of your calculation.

Thank you!!

Explanation / Answer

1. Moles= mass/Molar mass= 5/53.49= 0.0934 ( B is correct)

2, qcal= mass* specific heat* temperature difference

mass of water= volume*density= 25ml*1g/ml= 25 gm, mass of NH4Cl= 5 gm

total mass= 30 gm, specific heat is assumed same as that of water= 4.2 J/gm.deg.c

Qcal = 30*4.2*(9.1-21.5)=-1562 Joules ( close answer is -1740 Joules)

3. temperature change = 9.1-21.5= -12.4 deg.c

4. It is as per calculations, -1562 joules ,but close answe is -1740 Joules

5.

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