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For a given gas at 1 atm pressure, rms s...

For a given gas at 1 atm pressure, rms speed of the molecules is `200 m//s` at `127^(@)C`. At 2 atm pressure and at `227^(@)C`, the speed of the molecules will be :

A

`100 m//s`

B

`80 sqrt(5)m//s`

C

`100 sqrt(5)m//s`

D

`80 m//s`

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem, we need to find the root mean square (RMS) speed of gas molecules at different pressures and temperatures. The formula for RMS speed is given by: \[ V_{rms} = \sqrt{\frac{3RT}{M}} \] where: - \( V_{rms} \) is the root mean square speed, - \( R \) is the universal gas constant, - \( T \) is the absolute temperature in Kelvin, - \( M \) is the molar mass of the gas. ### Step-by-Step Solution: 1. **Convert Temperatures to Kelvin:** - The initial temperature \( T_1 = 127^\circ C = 127 + 273 = 400 \, K \) - The final temperature \( T_2 = 227^\circ C = 227 + 273 = 500 \, K \) 2. **Write the RMS Speed Formula for Both Conditions:** - For the first condition (1 atm, 400 K): \[ V_1 = \sqrt{\frac{3R \cdot 400}{M}} = 200 \, m/s \] - For the second condition (2 atm, 500 K): \[ V_2 = \sqrt{\frac{3R \cdot 500}{M}} \] 3. **Relate the Two Speeds:** - Since \( V_{rms} \) is proportional to the square root of temperature and inversely proportional to the square root of pressure, we can write: \[ \frac{V_2}{V_1} = \sqrt{\frac{T_2 \cdot P_1}{T_1 \cdot P_2}} \] - Here, \( P_1 = 1 \, atm \) and \( P_2 = 2 \, atm \). 4. **Substituting the Values:** - Substitute \( T_1 = 400 \, K \), \( T_2 = 500 \, K \), \( P_1 = 1 \, atm \), and \( P_2 = 2 \, atm \): \[ \frac{V_2}{200} = \sqrt{\frac{500 \cdot 1}{400 \cdot 2}} \] 5. **Calculating the Right Side:** - Calculate the fraction: \[ \frac{500}{800} = \frac{5}{8} \] - Therefore: \[ \frac{V_2}{200} = \sqrt{\frac{5}{8}} \] 6. **Finding \( V_2 \):** - Multiply both sides by 200: \[ V_2 = 200 \cdot \sqrt{\frac{5}{8}} = 200 \cdot \frac{\sqrt{5}}{2\sqrt{2}} = 100\sqrt{5} \] ### Final Answer: \[ V_2 = 100\sqrt{5} \, m/s \]
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