14.5 The following table lists molecular weight data O for a polytetrafluoroethylene material. Compute the following: (a) the number-average molecular weight (b) the weight-average molecular weight (c) the degree of polymerization Molecular Weight Range (g/mol) X; W; 10,000-20,000 0.03 0.01 20,000-30,000 0.09 0.04 30,000-40,000 0.15 0.11 40,000-50,000 0.25 0.23 50,000-60,000 0.22 0.24 60,000-70,000 0.14 0.18 70,000-80,000 0.08 0.12 80,000-90,000 0.04 0.07

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### Molecular Weight Analysis of Polytetrafluoroethylene

The following table provides molecular weight data for a polytetrafluoroethylene material. You are asked to compute:

(a) The number-average molecular weight  
(b) The weight-average molecular weight  
(c) The degree of polymerization  

#### Table: Molecular Weight Distribution

| Molecular Weight Range (g/mol) | \( x_i \) | \( w_i \) |
|----------------------------------|-----------|-----------|
| 10,000–20,000                  | 0.03      | 0.01      |
| 20,000–30,000                  | 0.09      | 0.04      |
| 30,000–40,000                  | 0.15      | 0.11      |
| 40,000–50,000                  | 0.25      | 0.23      |
| 50,000–60,000                  | 0.22      | 0.24      |
| 60,000–70,000                  | 0.14      | 0.18      |
| 70,000–80,000                  | 0.06      | 0.12      |
| 80,000–90,000                  | 0.04      | 0.07      |

- **\( x_i \)** represents the mole fraction.
- **\( w_i \)** denotes the weight fraction.

To compute the number-average molecular weight, \( M_n \):

\[ M_n = \frac{\Sigma (x_i M_i)}{\Sigma x_i} \]

For the weight-average molecular weight, \( M_w \):

\[ M_w = \frac{\Sigma (w_i M_i)}{\Sigma w_i} \]

The degree of polymerization can be calculated using:

\[ \text{Degree of Polymerization} = \frac{M_n}{M_0} \]

Where \( M_0 \) is the molecular weight of the monomer unit.

These computations will help characterize the polymer's molecular distribution, affecting its physical and chemical properties.
Transcribed Image Text:### Molecular Weight Analysis of Polytetrafluoroethylene The following table provides molecular weight data for a polytetrafluoroethylene material. You are asked to compute: (a) The number-average molecular weight (b) The weight-average molecular weight (c) The degree of polymerization #### Table: Molecular Weight Distribution | Molecular Weight Range (g/mol) | \( x_i \) | \( w_i \) | |----------------------------------|-----------|-----------| | 10,000–20,000 | 0.03 | 0.01 | | 20,000–30,000 | 0.09 | 0.04 | | 30,000–40,000 | 0.15 | 0.11 | | 40,000–50,000 | 0.25 | 0.23 | | 50,000–60,000 | 0.22 | 0.24 | | 60,000–70,000 | 0.14 | 0.18 | | 70,000–80,000 | 0.06 | 0.12 | | 80,000–90,000 | 0.04 | 0.07 | - **\( x_i \)** represents the mole fraction. - **\( w_i \)** denotes the weight fraction. To compute the number-average molecular weight, \( M_n \): \[ M_n = \frac{\Sigma (x_i M_i)}{\Sigma x_i} \] For the weight-average molecular weight, \( M_w \): \[ M_w = \frac{\Sigma (w_i M_i)}{\Sigma w_i} \] The degree of polymerization can be calculated using: \[ \text{Degree of Polymerization} = \frac{M_n}{M_0} \] Where \( M_0 \) is the molecular weight of the monomer unit. These computations will help characterize the polymer's molecular distribution, affecting its physical and chemical properties.
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