Answer to Question 2

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(a) the rms speed of the molecules;     

 

p = 1/3 r<c2

1.0 105 Pa = 1/3 1.25 kg m-3 <c2>  

 

<c2> = 3 1.0 105 Pa = 240 000 m2 s-2

                       1.25 kg m-3  

 

Rms speed =     490 m s-1

                                                                

 

(b) the temperature at which the molecules travel twice as fast. 

 

  • The kinetic energy is proportional to the temperature.  If we double the speed, the kinetic energy goes up by 4 times, therefore the temperature goes up 4 times.

  • 27 oC = 300 K

  • New temperature = 1200 K

 

 

Did you forget to convert Celsius to Kelvin?