The freezing point of water H₂O is 0.00 °C at 1 atmosphere. A nonvolatile, nonelectrolyte that dissolves in water is glucose. How many grams of glucose, C6H12O6 (180.2 g/mol), must be dissolved in 218.0 grams of water to reduce the freezing point by 0.350 °C? Refer to the table for the necessary boiling or freezing point constant. Solvent Formula Kb (°C/m) Kf(°C/m) Water H₂O 0.512 Ethanol CH3 CH₂OH 1.22 Chloroform CHC13 3.67 Benzene C6H6 2.53 Diethyl ether CH3 CH₂ OCH₂ CH3 2.02 Mass= g 1.86 1.99 5.12

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**Boiling Point Elevation/Freezing Point Depression**

\[ \Delta T = m \, K \]

- **For freezing point depression:**

  \[ \Delta T = T(\text{pure solvent}) - T(\text{solution}) \]

- **For boiling point elevation:**

  \[ \Delta T = T(\text{solution}) - T(\text{pure solvent}) \]

Where:
- \( m = \) (# moles solute / Kg solvent)
- \( K_b = \) boiling point elevation constant
- \( K_f = \) freezing point depression constant

\( K_b \) and \( K_f \) depend only on the SOLVENT. Below are some common values. Use these values for the calculations that follow.

| Solvent      | Formula        | \( K_b (°C / m) \) | \( K_f (°C / m) \) |
|--------------|----------------|------------------|------------------|
| Water        | H\(_2\)O         | 0.512            | 1.86             |
| Ethanol      | CH\(_3\)CH\(_2\)OH | 1.22             | 1.99             |
| Chloroform   | CHCl\(_3\)      | 3.67             | -                |
| Benzene      | C\(_6\)H\(_6\)       | 2.53             | 5.12             |
| Diethyl ether| CH\(_3\)CH\(_2\)OCH\(_2\)CH\(_3\) | 2.02             | -                |
Transcribed Image Text:**Boiling Point Elevation/Freezing Point Depression** \[ \Delta T = m \, K \] - **For freezing point depression:** \[ \Delta T = T(\text{pure solvent}) - T(\text{solution}) \] - **For boiling point elevation:** \[ \Delta T = T(\text{solution}) - T(\text{pure solvent}) \] Where: - \( m = \) (# moles solute / Kg solvent) - \( K_b = \) boiling point elevation constant - \( K_f = \) freezing point depression constant \( K_b \) and \( K_f \) depend only on the SOLVENT. Below are some common values. Use these values for the calculations that follow. | Solvent | Formula | \( K_b (°C / m) \) | \( K_f (°C / m) \) | |--------------|----------------|------------------|------------------| | Water | H\(_2\)O | 0.512 | 1.86 | | Ethanol | CH\(_3\)CH\(_2\)OH | 1.22 | 1.99 | | Chloroform | CHCl\(_3\) | 3.67 | - | | Benzene | C\(_6\)H\(_6\) | 2.53 | 5.12 | | Diethyl ether| CH\(_3\)CH\(_2\)OCH\(_2\)CH\(_3\) | 2.02 | - |
### Freezing Point Depression Example

The freezing point of water \( \text{H}_2\text{O} \) is 0.00 °C at 1 atmosphere. A nonvolatile, nonelectrolyte solute that dissolves in water is glucose.

**Problem:**
How many grams of glucose, \( \text{C}_6\text{H}_{12}\text{O}_6 \) (180.2 g/mol), must be dissolved in 218.0 grams of water to reduce the freezing point by 0.350 °C? Refer to the table for the necessary boiling or freezing point constant.

**Table: Freezing and Boiling Point Constants**

The table below shows various solvents along with their chemical formulas and constants:

| Solvent       | Formula              | \( K_b \) (°C/m) | \( K_f \) (°C/m) |
|---------------|----------------------|------------------|------------------|
| Water         | \( \text{H}_2\text{O} \)           | 0.512            | 1.86             |
| Ethanol       | \( \text{CH}_3\text{CH}_2\text{OH} \) | 1.22             | 1.99             |
| Chloroform    | \( \text{CHCl}_3 \)                | 3.67             |                  |
| Benzene       | \( \text{C}_6\text{H}_6 \)          | 2.53             | 5.12             |
| Diethyl ether | \( \text{CH}_3\text{CH}_2\text{OCH}_2\text{CH}_3 \) | 2.02             |                  |

### Calculate

To calculate the mass of glucose needed, use the freezing point depression formula:

\[
\Delta T_f = i \times K_f \times m
\]

Where:
- \( \Delta T_f \) is the change in freezing point (0.350 °C)
- \( i \) is the van't Hoff factor (1 for glucose since it doesn’t dissociate)
- \( K_f \) is the freezing point depression constant for water (1.86 °C/m)
- \( m \) is the molality of the solution

**Calculate the molality (\( m \)):**

Re
Transcribed Image Text:### Freezing Point Depression Example The freezing point of water \( \text{H}_2\text{O} \) is 0.00 °C at 1 atmosphere. A nonvolatile, nonelectrolyte solute that dissolves in water is glucose. **Problem:** How many grams of glucose, \( \text{C}_6\text{H}_{12}\text{O}_6 \) (180.2 g/mol), must be dissolved in 218.0 grams of water to reduce the freezing point by 0.350 °C? Refer to the table for the necessary boiling or freezing point constant. **Table: Freezing and Boiling Point Constants** The table below shows various solvents along with their chemical formulas and constants: | Solvent | Formula | \( K_b \) (°C/m) | \( K_f \) (°C/m) | |---------------|----------------------|------------------|------------------| | Water | \( \text{H}_2\text{O} \) | 0.512 | 1.86 | | Ethanol | \( \text{CH}_3\text{CH}_2\text{OH} \) | 1.22 | 1.99 | | Chloroform | \( \text{CHCl}_3 \) | 3.67 | | | Benzene | \( \text{C}_6\text{H}_6 \) | 2.53 | 5.12 | | Diethyl ether | \( \text{CH}_3\text{CH}_2\text{OCH}_2\text{CH}_3 \) | 2.02 | | ### Calculate To calculate the mass of glucose needed, use the freezing point depression formula: \[ \Delta T_f = i \times K_f \times m \] Where: - \( \Delta T_f \) is the change in freezing point (0.350 °C) - \( i \) is the van't Hoff factor (1 for glucose since it doesn’t dissociate) - \( K_f \) is the freezing point depression constant for water (1.86 °C/m) - \( m \) is the molality of the solution **Calculate the molality (\( m \)):** Re
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