Question

The root mean square speed of smoke particles of mass 5 × 10^-17 in their Brownian motion in air at NTP is approximately. [Given k = 1.38 × 10^-23 JK^-1]

• A. 60 mm s^-1
• B. 12 mm s-1
• C. 15 mm s-1
• D. 36 mm s-1

Answer 1

The Correct Option is C

At NTP, T=298 K
⇒v_rms=\(\sqrt\frac{3RT}{M}\)
\(=\sqrt{\frac{3kN_A×298}{5×10^{−17}×N_A}}\)
≃15 mm/s
So, the correct option is (C): 15 mm s^-1