Question

Under 3 atm, 12.5 litre of a certain gas weight 15g, calculate the average speed of gaseous molecules.

• A. $7\times {10}^{4}cmse{c}^{-1}$
• B. $8.028\times {10}^{4}cmse{c}^{-1}$
  
• C. $6\times {10}^{5}cmse{c}^{-1}$
• D. $8.028\times {10}^{6}cmse{c}^{-1}$

Answer 1

The correct option is B $8.028\times {10}^{4}cmse{c}^{-1}$

Pressure = 3 atm

Volume = 12.5 litre

Weight = 15 g

For gas we have$PV$ = $\frac{w}{m}RT$

$3\times 12.5$ = $\frac{15}{m}RT$ $\times 0.0821\times T$

$\frac{T}{m}$ = 30.45

$U_A$${}_V$ = $\sqrt{\frac{8RT}{\pi m}}$

= $\sqrt{\frac{8\times 8.314\times {10}^7\times 30.4\times 7}{\pi m}}$

= $8.028\times {10}^4$ cm $Se{c}^{-}$${}^1$