Root mean square velocity of a molecule is \(v\) at pressure \(P\). If pressure is increased two times, then the rms velocity becomes (A) \(3 \mathrm{~V}\) (B) \(2 \mathrm{v}\) (C) \(0.5 \mathrm{~V}\) (D) \(\mathrm{v}\)

Short Answer

Expert verified
In conclusion, the root mean square velocity when the pressure is increased two times is \(v'_{rms} = \sqrt{2}\cdot v_{rms}\). None of the given options (A, B, C, or D) are correct.

Step by step solution

01

1. Recall the root mean square speed formula

The root mean square speed (rms speed) is given by the following formula: \(v_{rms} = \sqrt{\frac{3kT}{m}}\) where: - \(v_{rms}\) is the root mean square speed - \(k\) is the Boltzmann constant - \(T\) is the temperature in Kelvin - \(m\) is the mass of one molecule of the gas
02

2. Express the pressure in terms of the rms speed

We will use the ideal gas law to relate pressure to the rms speed. The ideal gas law is given by: \(PV = nRT\) where: - \(P\) is the pressure - \(V\) is the volume - \(n\) is the number of moles - \(R\) is the gas constant - \(T\) is the temperature in Kelvin Since the number of molecules \(N\) is related to the number of moles \(n\) by the formula \(N = nN_A\), where \(N_A\) is Avogadro's number, we can write the ideal gas law as: \(PV = \frac{NkT}{N_A}\) Now, we can write the pressure formula in terms of the rms speed: \(P = \frac{Nkm}{N_A} \cdot \frac{v_{rms}^2}{3}\) where we have replaced the temperature \(T\) by the rms speed using the formula \(v_{rms}^2 = 3kT/m\)
03

3. Determine the new root mean square speed when the pressure is increased two times

Let's call the new pressure and rms speed \(P'\) and \(v'_{rms}\), respectively. The new pressure \(P'\) is two times the initial pressure \(P\): \(P' = 2P\) Now, with the new pressure and rms speed, the pressure formula becomes: \(P' = \frac{Nkm}{N_A}\cdot \frac{(v'_{rms})^2}{3}\) Since we already know that \(P' = 2P\), we can equate the two pressure formulas and solve for the new rms speed: \(\frac{Nkm}{N_A}\cdot \frac{(v'_{rms})^2}{3} = 2 \cdot \frac{Nkm}{N_A} \cdot \frac{v_{rms}^2}{3}\) By simplifying the equation, we get: \((v'_{rms})^2 = 2\cdot(v_{rms})^2\) Finally, we take the square root of both sides: \(v'_{rms} = \sqrt{2}\cdot v_{rms}\) Since \(\sqrt{2}\) is not equal to any of the given options, we can conclude that none of the given options (A, B, C, or D) are correct.

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