To determine the integral heat of solution of ammonium chloride (\(\Delta H_{sol}\)) by the calorimetric method.
Apparatus and Reagents:
* Calorimeter
* Thermometer
* Magnetic stirrer
* Analytical balance
* Ammonium chloride (NH4Cl)
* Distilled water
Procedure:
1. Clean and dry the calorimeter and its accessories.
2. Weigh about 1.0-1.5 g of ammonium chloride accurately using an analytical balance and transfer it to the calorimeter.
3. Add a known volume (50-100 mL) of distilled water to the calorimeter and stir the solution continuously using a magnetic stirrer.
4. Record the initial temperature (\(T_i\)) of the solution.
5. Wait until the temperature reaches a constant value (\(T_f\)) and record it.
6. Calculate the heat absorbed (\(q_{sol}\)) by the solution using the equation:
\(q_{sol} = m_{sol} \times C_{sol} \times (T_f - T_i)\)
- Where \(m_{sol}\) is the mass of the solution (g), \(C_{sol}\) is the specific heat capacity of the solution (J/g °C), and \((T_f - T_i)\) is the temperature change (°C).
7. Calculate the number of moles of ammonium chloride dissolved (\(n_{NH_4Cl}\)) using its molar mass (\(53.49\ g/mol\)).
\(n_{NH_4Cl} = m_{NH_4Cl} / M_{NH_4Cl}\)
8. Calculate the integral heat of solution (\(\Delta H_{sol}\)) in \(kJ/mol\) using the equation:
\(\Delta H_{sol} = (q_{sol}/n_{NH_4Cl})/1000\)
Note:
* Ensure proper insulation of the calorimeter to minimize heat loss to the surroundings.
* Use a well-calibrated thermometer to obtain accurate temperature measurements.
* Repeat the experiment multiple times to obtain reliable results.
Expected Results:
The integral heat of solution of ammonium chloride (\(\Delta H_{sol}\)) is approximately -31.4 kJ/mol.
The negative sign indicates that the dissolution process is exothermic, releasing heat to the surroundings.
