Part D Application of Hess's Law a. Write in your experimentally-derived enthalpy values in the following thermochemical equations. (1) Mg(s) + 2 HCl(aq) → MgCl₂(aq) + H₂(g) (2) Mg0(s) + 2 HCl(aq) → MgCl₂(aq) + H₂O(1) ΔΗ, ΔΗ2 = b. Use Hess's Law to get AH3 for reaction (3) from AH₁ and AH2. (3) Mg(s) + H₂O(1)→ MgO(s) + H₂(g) AH3 = c. Now calculate AH3 from standard molar enthalpies of formation found in the thermodynamic tables in the appendix.

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For part A B & C do calculations and write the missing numbers in the tables
**Part D: Application of Hess’s Law**

a. **Write in your experimentally-derived enthalpy values in the following thermochemical equations.**
   1. \( \text{Mg(s)} + 2 \text{HCl(aq)} \rightarrow \text{MgCl}_2\text{(aq)} + \text{H}_2\text{(g)} \) \hspace{10pt} \( \Delta H_1 = \underline{\hspace{50pt}} \)
   2. \( \text{MgO(s)} + 2 \text{HCl(aq)} \rightarrow \text{MgCl}_2\text{(aq)} + \text{H}_2\text{O(l)} \) \hspace{10pt} \( \Delta H_2 = \underline{\hspace{50pt}} \)

b. **Use Hess’s Law to get \( \Delta H_3 \) for reaction (3) from \( \Delta H_1 \) and \( \Delta H_2 \).**
   3. \( \text{Mg(s)} + \text{H}_2\text{O(l)} \rightarrow \text{MgO(s)} + \text{H}_2\text{(g)} \) \hspace{10pt} \( \Delta H_3 = \underline{\hspace{50pt}} \)

c. **Now calculate \( \Delta H_3 \) from standard molar enthalpies of formation found in the thermodynamic tables in the appendix.**

d. **Discussion: Compare your experimental value of \( \Delta H_3 \) with the value calculated from the thermodynamic tables. Can you explain why they shouldn’t be exactly the same?**

In this exercise, you will apply Hess's Law to calculate the enthalpy of a reaction (\( \Delta H_3 \)) by using experimentally-derived values (\( \Delta H_1 \) and \( \Delta H_2 \)) and then compare these values with those calculated from standard thermodynamic tables. This process involves analyzing potential discrepancies and understanding potential sources of experimental error.
Transcribed Image Text:**Part D: Application of Hess’s Law** a. **Write in your experimentally-derived enthalpy values in the following thermochemical equations.** 1. \( \text{Mg(s)} + 2 \text{HCl(aq)} \rightarrow \text{MgCl}_2\text{(aq)} + \text{H}_2\text{(g)} \) \hspace{10pt} \( \Delta H_1 = \underline{\hspace{50pt}} \) 2. \( \text{MgO(s)} + 2 \text{HCl(aq)} \rightarrow \text{MgCl}_2\text{(aq)} + \text{H}_2\text{O(l)} \) \hspace{10pt} \( \Delta H_2 = \underline{\hspace{50pt}} \) b. **Use Hess’s Law to get \( \Delta H_3 \) for reaction (3) from \( \Delta H_1 \) and \( \Delta H_2 \).** 3. \( \text{Mg(s)} + \text{H}_2\text{O(l)} \rightarrow \text{MgO(s)} + \text{H}_2\text{(g)} \) \hspace{10pt} \( \Delta H_3 = \underline{\hspace{50pt}} \) c. **Now calculate \( \Delta H_3 \) from standard molar enthalpies of formation found in the thermodynamic tables in the appendix.** d. **Discussion: Compare your experimental value of \( \Delta H_3 \) with the value calculated from the thermodynamic tables. Can you explain why they shouldn’t be exactly the same?** In this exercise, you will apply Hess's Law to calculate the enthalpy of a reaction (\( \Delta H_3 \)) by using experimentally-derived values (\( \Delta H_1 \) and \( \Delta H_2 \)) and then compare these values with those calculated from standard thermodynamic tables. This process involves analyzing potential discrepancies and understanding potential sources of experimental error.
## Calorimetry Experiment Data

### Part A: Calorimeter Constant

**Trials: 1**

- **Temperature of 50.0 mL cool water (Tc):** 18.8°C
- **Temperature of 50.0 mL warm water (Th):** 80.0°C
- **Maximum temperature on mixing (T2):** 52.8°C
- **Heat capacity of calorimeter (J/°C):** 
- **Average heat capacity of calorimeter (J/°C):** 

*Instruction:* Show a sample calculation of the heat capacity of the calorimeter for one run. Show both values and the average in the table above. In the calculations for Parts B and C, use C_cal = 0 if your average heat capacity is negative.

### Part B: Mg plus HCl

**Trials: 1**

- **Mass of magnesium:** 0.1490g
- **Initial temperature of HCl (T1):** 19.4°C
- **Final (maximum) temperature (T2):** 35.1°C
- **ΔT = T2 - T1:** 
- **ΔH (kJ/mol Mg):** 
- **Average value of ΔH (kJ/mol Mg):** 

### Part C: MgO plus HCl

**Trials: 1**

- **Mass of weighing dish plus MgO:** 0.8182g
- **Mass weighing dish after use:** 0.5691g
- **Net mass of MgO taken for reaction:** 0.2491g
- **Initial temperature of HCl (T1):** 18.5°C
- **Final (maximum) temperature (T2):** 
- **ΔT = T2 - T1:** 
- **ΔH (kJ/mol MgO):** 
- **Average value of ΔH (kJ/mol MgO):**

*Instruction:* In your notebook, show a sample calculation of the heat of reaction for one run for Parts B and C. Show both values and the average in the tables above. Assume 50.0g, with c_solution = 4.18 J/g°C.
Transcribed Image Text:## Calorimetry Experiment Data ### Part A: Calorimeter Constant **Trials: 1** - **Temperature of 50.0 mL cool water (Tc):** 18.8°C - **Temperature of 50.0 mL warm water (Th):** 80.0°C - **Maximum temperature on mixing (T2):** 52.8°C - **Heat capacity of calorimeter (J/°C):** - **Average heat capacity of calorimeter (J/°C):** *Instruction:* Show a sample calculation of the heat capacity of the calorimeter for one run. Show both values and the average in the table above. In the calculations for Parts B and C, use C_cal = 0 if your average heat capacity is negative. ### Part B: Mg plus HCl **Trials: 1** - **Mass of magnesium:** 0.1490g - **Initial temperature of HCl (T1):** 19.4°C - **Final (maximum) temperature (T2):** 35.1°C - **ΔT = T2 - T1:** - **ΔH (kJ/mol Mg):** - **Average value of ΔH (kJ/mol Mg):** ### Part C: MgO plus HCl **Trials: 1** - **Mass of weighing dish plus MgO:** 0.8182g - **Mass weighing dish after use:** 0.5691g - **Net mass of MgO taken for reaction:** 0.2491g - **Initial temperature of HCl (T1):** 18.5°C - **Final (maximum) temperature (T2):** - **ΔT = T2 - T1:** - **ΔH (kJ/mol MgO):** - **Average value of ΔH (kJ/mol MgO):** *Instruction:* In your notebook, show a sample calculation of the heat of reaction for one run for Parts B and C. Show both values and the average in the tables above. Assume 50.0g, with c_solution = 4.18 J/g°C.
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