Question

. The average molecular speed is greatest in which of the following gas samples ?
(1) 1.0 mol of O2 at 560 K
(2) 0.50 mol of Ne at 500 K
(3) 0.20 mol of CO2 at 440 K
X4) 2.0 mol of He at 140 K​

Answer 1

The average molecular speed is greatest in 2.0 moles of He at 140K

• The average molecular speed is given by the formula  $c = \sqrt{\frac{8RT}{\pi M} }$

• The average speed of the molecules depends on the value of   $\sqrt{\frac{T}{M} }$ .The greater the value the higher is the speed.

• For O₂ at 560K

                $\sqrt{\frac{T}{M} }= \sqrt{\frac{560}{32} }=4.18$

• For Ne at 500K

               $\sqrt{\frac{T}{M} }= \sqrt{\frac{500}{20} }=5$

• For CO₂ a t440K

               $\sqrt{\frac{T}{M} }= \sqrt{\frac{440}{44} }=3.16$

• For He at 140K

               $\sqrt{\frac{T}{M} }= \sqrt{\frac{140}{4} }=5.91$

• As the value is greater for He the average molecular speed is greater for 2.0 moles of He at 140K.