A student prepares a solution by dissolving 2.09 g of para-dichlorobenzene (CçH_C,, M = 147.0 g/mol) in 50.0 mL of cyclohexane. What is the freezing point (in °C) of the prepared solution? Pure cyclohexane has a freezing point of 6.47°C, a freezing point depression constant of 20.0°C/m, and a density of 1.25 g/mL. Freezing point PC %3D

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### Freezing Point Depression Calculation

A student prepares a solution by dissolving 2.09 g of para-dichlorobenzene (C₆H₄Cl₂, \( M = 147.0 \, \text{g/mol} \)) in 50.0 mL of cyclohexane. What is the freezing point (in °C) of the prepared solution? Pure cyclohexane has a freezing point of 6.47°C, a freezing point depression constant of 20.0°C/m, and a density of 1.25 g/mL.

#### Calculation Steps

1. **Determine the molality (m) of the solution:**
   - First, calculate the moles of para-dichlorobenzene:
     \[
     \text{Moles of para-dichlorobenzene} = \frac{2.09 \, \text{g}}{147.0 \, \text{g/mol}} = 0.01423 \, \text{mol}
     \]
   - Convert the volume of cyclohexane from mL to kg:
     \[
     50.0 \, \text{mL} \times 1.25 \, \text{g/mL} = 62.5 \, \text{g} = 0.0625 \, \text{kg}
     \]
   - Calculate the molality (m):
     \[
     \text{molality} = \frac{0.01423 \, \text{mol}}{0.0625 \, \text{kg}} = 0.22768 \, \text{m}
     \]

2. **Apply the freezing point depression formula:**
   \[
   \Delta T_f = K_f \times m
   \]
   Where:
   - \( \Delta T_f \) is the freezing point depression.
   - \( K_f \) is the freezing point depression constant (20.0°C/m).
   - \( m \) is the molality of the solution calculated above.
     \[
     \Delta T_f = 20.0 \, \frac{°C}{m} \times 0.22768 \, m = 4.5536 \, °C
     \]

3. **Determine the new freezing point of the solution:**
Transcribed Image Text:### Freezing Point Depression Calculation A student prepares a solution by dissolving 2.09 g of para-dichlorobenzene (C₆H₄Cl₂, \( M = 147.0 \, \text{g/mol} \)) in 50.0 mL of cyclohexane. What is the freezing point (in °C) of the prepared solution? Pure cyclohexane has a freezing point of 6.47°C, a freezing point depression constant of 20.0°C/m, and a density of 1.25 g/mL. #### Calculation Steps 1. **Determine the molality (m) of the solution:** - First, calculate the moles of para-dichlorobenzene: \[ \text{Moles of para-dichlorobenzene} = \frac{2.09 \, \text{g}}{147.0 \, \text{g/mol}} = 0.01423 \, \text{mol} \] - Convert the volume of cyclohexane from mL to kg: \[ 50.0 \, \text{mL} \times 1.25 \, \text{g/mL} = 62.5 \, \text{g} = 0.0625 \, \text{kg} \] - Calculate the molality (m): \[ \text{molality} = \frac{0.01423 \, \text{mol}}{0.0625 \, \text{kg}} = 0.22768 \, \text{m} \] 2. **Apply the freezing point depression formula:** \[ \Delta T_f = K_f \times m \] Where: - \( \Delta T_f \) is the freezing point depression. - \( K_f \) is the freezing point depression constant (20.0°C/m). - \( m \) is the molality of the solution calculated above. \[ \Delta T_f = 20.0 \, \frac{°C}{m} \times 0.22768 \, m = 4.5536 \, °C \] 3. **Determine the new freezing point of the solution:**
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