Act like a helpful tutor and exlain me : Give step-by-step solution with explanation and final answer:4. A polymer specimen has a viscosity of 1 Pa.s at room temperature. If the activation energy of the atomic process responsible for viscosity is 10 kJ/mol, what is the viscosity of this polymer at 100°C? (10 points)
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Act like a helpful tutor and exlain me :
Give step-by-step solution with explanation and final answer:4. A polymer specimen has a viscosity of 1 Pa.s at room temperature. If the activation
energy of the atomic process responsible for viscosity is 10 kJ/mol, what is the viscosity
of this polymer at 100°C? (10 points)
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Asked by: manish kumar
Created at: 2025-09-24 02:19:15
Asked by: manish kumar
Created at: 2025-09-24 02:19:15
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## Step-by-Step Solution
Let's break down the problem and solve it step by step.
### **Given Data**
- Viscosity at room temperature (\(\eta_1\)): **1 Pa·s**
- Room temperature (\(T_1\)): **Assume 25°C = 298 K**
- Temperature at which to find viscosity (\(T_2\)): **100°C = 373 K**
- Activation energy (\(Q\)): **10 kJ/mol = 10,000 J/mol**
- Gas constant (\(R\)): **8.314 J/(mol·K)**
---
### **Step 1: The Viscosity-Temperature Relationship**
Viscosity \(\eta\) changes with temperature according to the **Arrhenius equation**:
\[
\eta = A \exp\left(\frac{Q}{RT}\right)
\]
Taking the ratio at two temperatures:
\[
\frac{\eta_2}{\eta_1} = \exp\left( \frac{Q}{R} \left(\frac{1}{T_2} - \frac{1}{T_1}\right) \right)
\]
---
### **Step 2: Plug in the Values**
- \(Q = 10,000\) J/mol
- \(R = 8.314\) J/(mol·K)
- \(T_1 = 298\) K (room temperature)
- \(T_2 = 373\) K (100°C)
\[
\frac{\eta_2}{\eta_1} = \exp\left( \frac{10,000}{8.314} \left(\frac{1}{373} - \frac{1}{298}\right) \right)
\]
---
### **Step 3: Calculate the Exponent**
#### **a) Calculate \( \frac{1}{T_2} - \frac{1}{T_1} \):**
\[
\frac{1}{373} - \frac{1}{298} = 0.002681 - 0.003356 = -0.000675 \; \text{K}^{-1}
\]
#### **b) Calculate \( \frac{Q}{R} \):**
\[
\frac{Q}{R} = \frac{10,000}{8.314} = 1202.6
\]
#### **c) Multiply:**
\[
1202.6 \times (-0.000675) = -0.8118
\]
---
### **Step 4: Exponential Term**
\[
\exp(-0.8118) = 0.444
\]
---
### **Step 5: Find the Final Viscosity**
\[
\eta_2 = \eta_1 \times 0.444 = 1 \times 0.444 = 0.444 \text{ Pa·s}
\]
---
## **Final Answer**
\[
\boxed{0.44\ \text{Pa·s}}
\]
**(rounded to two decimal places)**
---
### **Summary Table**
| Temperature (°C) | Temperature (K) | Viscosity (Pa·s) |
|------------------|-----------------|------------------|
| 25 | 298 | 1.00 |
| 100 | 373 | 0.44 |
---
**Explanation:**
As temperature increases, the viscosity of the polymer decreases due to increased atomic/molecular motion, making it easier for the molecules to slide past each other.
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